Online Etymology Dictionary

put (n.): c. 1300, "act of throwing a weight overhand as a test of strength," from put (v.). General meaning "act of putting" is from early 15c. Also compare putt (n.).
lifeblood (n.): also life-blood, 1580s, "blood necessary for life," from life (n.) + blood (n.). Figurative and transferred use for "that which is essential to the life or strength of, that which gives vitality to" is from 1590s.
-cracy: word-forming element forming nouns meaning "rule or government by," from French -cratie or directly from Medieval Latin -cratia, from Greek -kratia "power, might; rule, sway; power over; a power, authority," from kratos "strength," from PIE *kre-tes- "power, strength," suffixed form of root *kar-/*ker- "hard" (see hard (adj.)). The connective -o- has come to be viewed as part of it. Productive in English from c. 1800.
effort (n.): late 15c., "laborious attempt, strenuous exertion," from Middle French effort, from Old French esforz "force, impetuosity, strength, power," verbal noun from esforcier "force out, exert oneself," from Vulgar Latin *exfortiare "to show strength" (source of Italian sforza), from Latin ex- "out" (see ex-) + Latin fortis "strong" (see fort).
Effort is only effort when it begins to hurt. [Ortega y Gasset, 1949]
Related: Efforts "voluntary exertion," also "result of exertion."
vigor (n.): c. 1300, "physical strength, energy in an activity," from Anglo-French vigour, Old French vigor "force, strength" (Modern French vigueur), from Latin vigorem (nominative vigor) "liveliness, activity, force," from vigere "be lively, flourish, thrive," from PIE root *weg- (2) "be lively or active" (see wake (v.)).
Hercules: Greek hero, son of Zeus and Alcmene, worshipped by the Romans as a god of strength, c. 1200 (originally in reference to the Pillars of Hercules), also Ercules, from Latin Hercles (Etruscan Hercle), from Greek Herakles, literally "Glory of Hera;" from Hera (q.v.) + kleos "glory, renown" (see Clio). Used figuratively in reference to strength since late 14c. Vocative form Hercule was a common Roman interjection (especially me Hercule!) "assuredly, certainly." The constellation so called in English by 1670s.
craft (n.): Old English cræft (West Saxon, Northumbrian), -creft (Kentish), originally "power, physical strength, might," from Proto-Germanic *krab-/*kraf- (source also of Old Frisian kreft, Old High German chraft, German Kraft "strength, skill;" Old Norse kraptr "strength, virtue"). Sense expanded in Old English to include "skill, dexterity; art, science, talent" (via a notion of "mental power"), which led by late Old English to the meaning "trade, handicraft, calling," also "something built or made." The word still was used for "might, power" in Middle English.

Use for "small boat" is first recorded 1670s, probably from a phrase similar to vessels of small craft and referring either to the trade they did or the seamanship they required, or perhaps it preserves the word in its original sense of "power."
debility (n.): early 15c., from Middle French debilite (Modern French débilité) or directly from Latin debilitatem (nominative debilitas) "a laming, crippling, weakening," from debilis "lame, disabled, crippled," figuratively "weak, helpless," from de- "from, away" (see de-) + -bilis "strength," from PIE root *bel- (see Bolshevik).
valence (n.): early 15c., "extract, preparation," from Latin valentia "strength, capacity," from valentem (nominative valens) "strong, stout, vigorous, powerful," present participle of valere "be strong" (see valiant). Meaning "relative combining capacity of an element" is recorded from 1884, from German Valenz (1868), from the Latin word. Related: Valency.
Fergus: masc. proper name, from Gaelic Fearghus or Old Irish Fergus "man-ability," first element cognate with Latin vir "man" (see virile); second from Old Irish gus "ability, excellence, strength, inclination," from Celtic root *gustu- "choice," from PIE root *geus- "to taste" (see gusto).
neuro-: before vowels neur-, word-forming element meaning "pertaining to a nerve or nerves or the nervous system," from Greek neuro-, comb. form of neuron "nerve," originally "sinew, tendon, cord, bowstring," also "strength, vigor," from PIE *(s)neu- "tendon, sinew" (see nerve).
alacrity (n.): mid-15c., from Latin alacritatem (nominative alacritas) "liveliness, ardor, eagerness," from alacer (genitive alacris) "cheerful, brisk, lively;" which is of uncertain origin, perhaps cognate with Gothic aljan "zeal," Old English ellen "courage, zeal, strength," Old High German ellian.
flange (n.): 1680s, "a widening or branching out," of unknown origin, perhaps related to Old French flanche "flank, hip, side," fem. of flanc (see flank (n.)). Meaning "projecting rim, etc., used for strength or guidance" is from 1735. As a verb from 1820.
overreach (v.): c. 1300, "to reach above or beyond" (transitive), from over- + reach (v.). Meaning "to extend over something, to cover it" is from c. 1400. Sense of "to reach beyond one's strength" is from 1560s. As a noun from 1550s. Related: Overreached; overreaching.
berserk (adj.): 1844, from berserk (n.) "Norse warrior," by 1835, an alternative form of berserker (1822), a word which was introduced by Sir Walter Scott, from Old Norse berserkr (n.) "raging warrior of superhuman strength;" probably from *ber- "bear" + serkr "shirt," thus literally "a warrior clothed in bearskin." Thus not from Old Norse berr "bare, naked."
Thorkelin, in the essay on the Berserkir, appended to his edition of the Krisini Saga, tells that an old name of the Berserk frenzy was hamremmi, i.e., strength acquired from another strange body, because it was anciently believed that the persons who were liable to this frenzy were mysteriously endowed, during its accesses, with a strange body of unearthly strength. If, however, the Berserk was called on by his own name, he lost his mysterious form, and his ordinary strength alone remained. ["Notes and Queries," Dec. 28, 1850]
The adjectival use probably is from such phrases as berserk frenzy, or as a title (Arngrim the Berserk).
formidable (adj.): mid-15c., "causing fear," from Middle French formidable (15c.), from Latin formidabilis "causing fear, terrible," from formidare "to fear," from formido "fearfulness, fear, terror, dread." Sense has softened somewhat over time, in the direction of "so great (in strength, size, etc.) as to discourage effort." Related: Formidably.
Humphrey: masc. proper name, from Old English Hunfrið, probably from Proto-Germanic *hun "strength" + Old English frið "peace." To dine with Duke Humphrey (17c.) meant to go without a meal, though the reason for the expression now is obscure.
brio (n.): "liveliness, vivacity," 1734, from Italian brio, literally "mettle, fire, life," perhaps a shortened derivative of Latin ebrius "drunk." Or via Provençal briu "vigor," from Celtic *brig-o- "strength," from PIE root *gwere- (2) "heavy" (see grave (adj.)). Probably entered English via musical instruction con brio.
prevalent (adj.): early 15c., "having great power or force," from Latin praevalentem (nominative praevalens) "of superior strength; mighty," present participle of praevalere "to be more able" (see prevail). Meaning "extensively existing, in general use" is from 1650s.
Samson: masc. proper name, Biblical strong-man (Judges xiii-xvi), from Late Latin, from Greek Sampson, from Hebrew Shimshon, probably from shemesh "sun." As a generic name for a man of great strength, attested from 1565. Samsonite, proprietary name for a make of luggage, is 1939, by Shwayder Bros. Inc., Denver, U.S.
enervate (v.): c. 1600, "deprive of force or strength," from Latin enervatus, past participle of enervare "to weaken" (see enervation). Literal sense of "to weaken, impair" in English is from 1610s. Related: Ennervated; ennervating. As a verb Middle English had enerve (c. 1400, eneruyd).
infirmity (n.): late 14c., "disease, sickness; lack of capability, weakness," from Latin infirmitatem (nominative infirmitas) "want of strength, weakness, feebleness," also "the weaker sex" [Lewis], noun of quality from infirmus "weak, frail" (see infirm). Perhaps in part from Middle French infirmité, Old French enfermete "illness, sickness, disease; moral weakness."
stiffen (v.): early 15c., "make steadfast," from stiff (adj.) + -en (1). Intransitive sense from 1690s. Earlier verb was simply stiff "gain strength, become strong" (late 14c.). Related: Stiffened; stiffener; stiffening. Compare German steifen "to stiffen."
force (n.): c. 1300, "physical strength," from Old French force "force, strength; courage, fortitude; violence, power, compulsion" (12c.), from Vulgar Latin *fortia (source also of Old Spanish forzo, Spanish fuerza, Italian forza), noun use of neuter plural of Latin fortis "strong, mighty; firm, steadfast; brave, bold" (see fort).

Meanings "power to convince the mind" and "power exerted against will or consent" are from mid-14c. Meaning "body of armed men, a military organization" first recorded late 14c. (also in Old French). Physics sense is from 1660s; force field attested by 1920. Related: Forces.
courage (n.): c. 1300, from Old French corage (12c., Modern French courage) "heart, innermost feelings; temper," from Vulgar Latin *coraticum (source of Italian coraggio, Spanish coraje), from Latin cor "heart," from PIE root *kerd- (1) "heart" (see heart (n.)) which remains a common metaphor for inner strength. In Middle English, used broadly for "what is in one's mind or thoughts," hence "bravery," but also "wrath, pride, confidence, lustiness," or any sort of inclination. Replaced Old English ellen, which also meant "zeal, strength."
virtue (n.): c. 1200, vertu, "moral life and conduct; a particular moral excellence," from Anglo-French and Old French vertu "force, strength, vigor; moral strength; qualities, abilities" (10c. in Old French), from Latin virtutem (nominative virtus) "moral strength, high character, goodness; manliness; valor, bravery, courage (in war); excellence, worth," from vir "man" (see virile).
For my part I honour with the name of virtue the habit of acting in a way troublesome to oneself and useful to others. [Stendhal "de l'Amour," 1822]
Especially (in women) "chastity, sexual purity" from 1590s. Phrase by virtue of (early 13c.) preserves alternative Middle English sense of "efficacy." Wyclif Bible has virtue where KJV uses power. The seven cardinal virtues (early 14c.) were divided into the natural (justice, prudence, temperance, fortitude) and the theological (hope, faith, charity). To make a virtue of a necessity (late 14c.) translates Latin facere de necessitate virtutem [Jerome].
calisthenics (n.): 1847 (calisthenic (adj.) is from 1839), formed on model of French callisthenie, from Latinized comb. form of Greek kallos "beauty" (see Callisto) + sthenos "strength" + -ics. Originally, gymnastic exercises suitable for girls and meant to develop the figure and promote graceful movement. The proper Greek, if there was such a word in Greek, would have been *kallistheneia.
fag (v.1): "to droop, decline in strength, become weary" (intransitive), 1520s, of uncertain origin; OED is content with the "common view" that it is an alteration of flag (v.) in its sense of "droop, go limp." Transitive sense of "to make (someone or something) fatigued, tire by labor" is first attested 1826. Related: Fagged; fagging.
feeble (adj.): late 12c., "lacking strength or vigor" (physical, moral, or intellectual), from Old French feble "weak, feeble" (12c., Modern French faible), dissimilated from Latin flebilis "lamentable," literally "that is to be wept over," from flere "weep, cry, shed tears, lament," from PIE *bhle- "to howl" (see bleat (v.)). The first -l- was lost in Old French. The noun meaning "feeble person" is recorded from mid-14c.
languish (v.): early 14c., "fail in strength, exhibit signs of approaching death," from languiss-, present participle stem of Old French languir "be listless, pine, grieve, fall ill" (12c.), from Vulgar Latin *languire, from Latin languere "be weak or faint" (see lax). Weaker sense of "be lovesick, grieve, lament, grow faint," is from mid-14c. Related: Languished; languishing.
main (adj.): early 13c., "large, bulky, strong," from Old English mægen- "power, strength, force," used in compounds (such as mægensibb "great love," mægenbyrðen "heavy burden;" see main (n.)), probably also from or influenced by Old Norse megenn (adj.) "strong, powerful." Sense of "chief" is c. 1400. Main course in the meal sense attested from 1829. Main man "favorite male friend; hero" is from 1967, African-American vernacular.
ochlocracy (n.): "government by the rabble," 1580s, from French ochlocratie (1560s), from Greek okhlokratia (Polybius) "mob rule," the lowest grade of democracy, from kratos "rule, power, strength" (see -cracy) + okhlos "mob, populace," perhaps literally "moving mass," from PIE *wogh-lo-, from root *wegh- "to go, transport" in a vehicle (see weigh). For sense development, compare mob (n.). Related: Ochlocratic; ochlocratical. Greek also had okhlagogos "mob-leader, ochlagogue."
unwieldy (adj.): late 14c., "lacking strength, powerless," from un- (1) "not" + obsolete wieldy, from Old English wielde "active, vigorous," from Proto-Germanic *walth- "have power" (see wield (v.)). Meaning "moving ungracefully" is recorded from 1520s; in reference to weapons, "difficult to handle, awkward by virtue of size or shape" it is attested from 1540s. Related: Unwieldiness.
valor (n.): c. 1300, "value, worth," from Old French valor, valour "valor, moral worth, merit, courage, virtue" (12c.), from Late Latin valorem (nominative valor) "value, worth" (in Medieval Latin "strength, valor"), from stem of Latin valere "be strong, be worth" (see valiant). The meaning "courage" is first recorded 1580s, from Italian valore, from the same Late Latin word. (The Middle English word also had a sense of "worth or worthiness in respect of manly qualities").
democracy (n.): 1570s, from Middle French démocratie (14c.), from Medieval Latin democratia (13c.), from Greek demokratia "popular government," from demos "common people," originally "district" (see demotic), + kratos "rule, strength" (see -cracy).
Democracy implies that the man must take the responsibility for choosing his rulers and representatives, and for the maintenance of his own 'rights' against the possible and probable encroachments of the government which he has sanctioned to act for him in public matters. [Ezra Pound, "ABC of Economics," 1933]
adjutant (n.): "military officer who assists superior officers," c. 1600, from Latin adiutantem (nominative adiutans), present participle of adiutare "to give help to, help zealously, serve," frequentative of adiuvare (past participle adiutus) "help, assist, aid, support," from ad- "to" (see ad-) + iuvare "to help, give strength, support," perhaps from same root as iuvenis "young person" (see young).
manual (adj.): c. 1400, from Latin manualis "of or belonging to the hand; that can be thrown by hand," from manus "hand, strength, power over; armed force; handwriting," from PIE *man- (2) "hand" (source also of Old Norse mund "hand," Old English mund "hand, protection, guardian," German Vormund "guardian," Greek mane "hand").
orgasm (n.): 1680s, "sexual climax," from French orgasme or Modern Latin orgasmus, from Greek orgasmos "excitement, swelling," from organ "be in heat, become ripe for," literally "to swell, be excited," related to orge "impulse, excitement, anger," from PIE root *wrog- "to burgeon, swell with strength" (source also of Sanskrit urja "a nourishment, sap, vigor," Old Irish ferc, ferg "anger"). Also used 17c. of other violent excitements of emotion or other bodily functions.
recover (v.): c. 1300, "to regain consciousness," from Anglo-French rekeverer (13c.), Old French recovrer "come back, return; regain health; procure, get again" (11c.), from Medieval Latin recuperare "to recover" (source of Spanish recobrar, Italian ricoverare; see recuperation). Meaning "to regain health or strength" is from early 14c.; sense of "to get (anything) back" is first attested mid-14c. Related: Recovered; recovering.
violation (n.): c. 1400, from Old French violacion and directly from Latin violationem (nominative violatio) "an injury, irreverence, profanation," from past participle stem of violare "to treat with violence, outrage, dishonor," perhaps an irregular derivative of vis "strength, force, power, energy," from PIE root *weie- "to go after, pursue with vigor or desire" (see gain (v.)).
virago (n.): late 14c., "man-like or heroic woman, woman of extraordinary stature, strength and courage," from Latin virago "female warrior, heroine, amazon," from vir "man" (see virile). Ælfric (c. 1000), following Vulgate, used it in Gen. ii:23 as the name Adam gave to Eve (KJV = woman):
Beo hire nama Uirago, þæt is, fæmne, forðan ðe heo is of hire were genumen.
Related: Viraginous.
Alexander: masc. proper name, from Latin, from Greek Alexandros "defender of men," from alexein "to ward off, keep off, turn (something) away, defend, protect" + aner (genitive andros) "man" (see anthropo-). The first element is related to Greek alke "protection, help, strength, power, courage," alkimos "strong;" cognate with Sanskrit raksati "protects," Old English ealgian "to defend." As a kind of cocktail, it is attested from 1930.
ephebic (adj.): 1880, from Latinized form of Greek ephebikos "of or for an ephebe," from ephebos "one arrived at puberty, one of age 18-20," from epi "upon" (see epi-) + hebe "early manhood," from PIE *yegw-a- "power, youth, strength." In classical Athens, a youth of 18 underwent his dokimasia, had his hair cut off, and was enrolled as a citizen. His chief occupation for the next two years was garrison duty.
theocracy (n.): 1737; earlier as un-Latinized theocraty (1620s), "form of government in which God is recognized as supreme ruler and his laws form the statute book," originally of the sacerdotal government of Israel before the rise of kings, from later Greek theokratia (Josephus), literally "the rule of God," from theos "god" (see theo-) + kratos "a rule, regime, strength" (see -cracy). Meaning "priestly or religious body wielding political and civil power" is recorded from 1825. Related: Theocratic (1741).
ambivalence (n.): "simultaneous conflicting feelings," 1924 (1912 as ambivalency), from German Ambivalenz, coined 1910 by Swiss psychologist Eugen Bleuler (1857-1939) on model of German Equivalenz "equivalence," etc., from Latin ambi- "both" (see ambi-) + valentia "strength," from present participle of valere "be strong" (see valiant). A psychological term that by 1929 had taken on a broader literary and general sense.
might (n.): Old English miht, earlier mæht "might, bodily strength, power, authority, ability," from Proto-Germanic *makhti- (source also of Old Norse mattr, Old Frisian, Middle Dutch, Dutch macht, Old High German maht, German Macht, Gothic mahts), Germanic suffixed form of PIE root *magh- (1) "be able, have power" (see may (v.)).
Mildred: fem. proper name, Old English Mildðryð, from milde "mild" (see mild) + ðryð "power, strength." A popular name in the Middle Ages through fame of St. Mildred (obit c. 700), abbess, daughter of a Mercian king and a Kentish princess. Among the 10 most popular names for girls born in the U.S. between 1903 and 1926, it hasn't been in the top 1,000 since 1983.
trapeze (n.): swing with a cross-bar, used for feats of strength and agility, 1861, from French trapèze, from Late Latin trapezium (see trapezium), probably because the crossbar, the ropes and the ceiling formed a trapezium.
The French, to whose powers of invention (so long as you do not insist upon utility) there is no limit, have invented for the world the Trapeze .... ["Chambers's Journal," July 6, 1861]
stamen (n.): "pollen-bearing organ of a flower," 1660s, from Modern Latin (1625, Spigelus), from Latin stamen "stamen" (Pliny), literally "foundation in weaving, thread of the warp" in the upright loom (related to stare "to stand"), from PIE *sta-men- (source also of Greek stemon "warp," also used by Hesychius for some part of a plant, Gothic stoma, Sanskrit sthaman "place," also "strength"), from root *stā- "to stand" (see stet). The usual English plural is stamens because of the special use of the classical plural, stamina.
augment (v.): c. 1400, from Old French augmenter "increase, enhance" (14c.), from Late Latin augmentare "to increase," from Latin augmentum "an increase," from augere "to increase, make big, enlarge, enrich," from PIE root *aug- (1) "to increase" (source also of Sanskrit ojas- "strength;" Lithuanian augu "to grow," aukstas "high, of superior rank;" Greek auxo "increase," auxein "to increase;" Gothic aukan "to grow, increase;" Old English eacien "to increase"). Related: Augmented; augmenting. As a noun from early 15c.