Online Etymology Dictionary

con (v.1): "to guide ships," 1620s, from French conduire "to conduct, lead, guide" (10c.), from Latin conducere (see conduce). Related: Conned; conning.
con (v.2): "to swindle," 1896, from con (adj.). Related: Conned; conning.
con (n.3): a slang or colloquial shortening of various nouns beginning in con-, such as, from the 19th century, confidant, conundrum, conformist, convict, contract, and from the 20th century, conductor, conservative.
con-: word-forming element meaning "together, with," sometimes merely intensive; the form of com- used in Latin before consonants except -b-, -p-, -l-, -m-, or -r-. In native English formations (such as costar), co- tends to be used where Latin would use con-.
conation (n.): in philosophical use from 1836, from Latin conationem (nominative conatio) "an endeavoring, effort," noun of action from past participle stem of conari "to endeavor, to try," from PIE *kona-, from root *ken- (1) "to set oneself in motion" (see deacon).
conative (adj.): 1836, from Latin conat-, past participle stem of conari "to endeavor, to try" (see conation) + -ive.
concatenate (v.): c. 1600, from Late Latin concatenatus, past participle of concatenare "to link together" (see concatenation). Related: Concatenated; concatenating.
concatenation (n.): c. 1600, from Late Latin concatenationem (nominative concatenatio) "a linking together," noun of action from past participle stem of concatenare "to link together," from com- "together" (see com-) + catenare, from catena "a chain" (see chain (n.)).
concave (adj.): early 15c., from Old French concave (14c.) or directly from Latin concavus "hollow, arched, vaulted, curved," from com-, intensive prefix (see com-), + cavus "hollow" (see cave (n.)).
concavity (n.): c. 1400, from Old French concavité "hollow, concavity" (14c.) or directly from Latin concavitatem (nominative concavitas), from Latin concavus "hollow" (see concave).
conceal (v.): early 14c., concelen, from Old French conceler "to hide, conceal, dissimulate," from Latin concelare "to hide," from com-, intensive prefix (see com-), + celare "to hide," from PIE root *kel- (2) "to cover, conceal" (see cell). Replaced Old English deagan. Related: Concealed; concealing.
concealment (n.): early 14c. (late 13c. in Anglo-French), from Old French concelement "concealment, secrecy," from conceler "to hide" (see conceal). Originally a term in law; general sense is from c. 1600.
concede (v.): 1630s, from Middle French concéder or directly from Latin concedere "give way, yield, go away, depart, retire," figuratively "agree, consent, give precedence," from com-, intensive prefix (see com-), + cedere "to go, grant, give way" (see cede). Related: Conceded; conceding.
conceit (n.): late 14c., "something formed in the mind, thought, notion," from conceiven (see conceive) based on analogy of deceit and receipt. Sense evolved from "something formed in the mind," to "fanciful or witty notion" (1510s), to "vanity" (c. 1600) through shortening of self-conceit (1580s).
conceited (adj.): c. 1600, "having an overweening opinion of oneself" (short for self-conceited, 1590s); earlier "having intelligence" (1540s); past participle adjective from conceit (q.v.).
conceivable (adj.): mid-15c. (implied in conceivableness), from conceive + -able. Originally in a now-obsolete sense "that can be received." Meaning "that can be imagined" is attested from 1620s (in conceivably).
conceive (v.): late 13c., conceiven, "take (seed) into the womb, become pregnant," from stem of Old French conceveir (Modern French concevoir), from Latin concipere (past participle conceptus) "to take in and hold; become pregnant," from com-, intensive prefix (see com-), + comb. form of capere "to take," from PIE *kap- "to grasp" (see capable). Meaning "take into the mind" is from mid-14c., a figurative sense also found in the Old French and Latin words. Related: Conceived; conceiving.
concent (n.): "harmony," 1580s, from Latin concentus "a singing together, harmony," from concinere "to sing or sound together," from com- "with, together" (see com-) + canere "to sing" (see chant (v.)). Often misspelled consent or confused with that word.
concentrate (v.): 1630s, "to bring or come to a common center," from concenter (1590s), from Italian concentrare, from Latin com- "together" (see com-) + centrum "center" (see center (n.)). Meaning "condense" is from 1680s. Sense of "mentally focus" is c. 1860. Related: Concentrated; concentrating.
concentrate (n.): 1883, from concentrate (v.).
concentration (n.): 1630s, "action of bringing to a center," noun of action from verb concentrate (v.). Meaning "a mass so collected" is from 1670s; "continuous focus of mental activity" is from 1846.
concentration camp (n.): 1901, "compound for noncombatants in a war zone" (see concentration); a term for a controversial idea in the second Boer War (1899-1902), and the term emerged with a bad odor.
The concentration camp now definitely taken its place side by side with Black Hole of Calcutta as one of those of horror at which humanity will never cease shudder. ["The Review of Reviews," London, March 1902]
It also was used 1902 in reference to then-current U.S. policies in the Philippines, and retroactively in reference to Spanish policies in Cuba during the insurrection there of 1896-98. The phrase was used in U.S. during the Spanish-American war, but in reference to designated rendezvous points for U.S. troops headed overseas. In reference to prisons for dissidents and minorities in Nazi Germany from 1934, in Soviet Russia from 1935.
concentric (adj.): c. 1400, from Middle French concentrique, from Medieval Latin concentricus, from com- "together" (see com-) + centrum "circle, center" (see center (n.)).
concept (n.): 1550s, from Medieval Latin conceptum "draft, abstract," in classical Latin "(a thing) conceived," from concep-, past participle stem of concipere "to take in" (see conceive). In some 16c. cases a refashioning of conceit (perhaps to avoid negative connotations).
conception (n.): early 14c., "act of conceiving," from Old French concepcion (Modern French conception) "conception, grasp, comprehension," from Latin conceptionem (nominative conceptio) "a comprehending, conception," noun of action from stem of concipere (see conceive). Originally in the womb sense (also with reference to Conception Day in the Church calendar); mental sense "process of forming concepts" is late 14c. Meaning "that which is conceived in the mind" is from 1520s; "general notion" is from 1785.
conceptive (adj.): 1630s, from Latin conceptivus, from conceptus, past participle of concipere (see conceive).
conceptual (adj.): 1820, "pertaining to mental conception" (there is an isolated use from 1662), from Medieval Latin conceptualis, from Latin conceptus "a collecting, gathering, conceiving," past participle of concipere (see conceive). Related: Conceptualism; conceptualist.
conceptualisation (n.): chiefly British English spelling of conceptualization; for spelling, see -ize.
conceptualise (v.): chiefly British English spelling of conceptualize; for suffix, see -ize. Related: Conceptualised; conceptualising.
conceptualization (n.): 1866; see conceptual + -ization. Perhaps based on French conceptualisation (1862).
conceptualize (v.): 1892, from conceptual + -ize. Related: Conceptualized; conceptualizing.
conceptually (adv.): 1842, from conceptual + -ly (2).
concern (v.): early 15c., "perceive, distinguish," also "refer to, relate to," from Middle French concerner, from Medieval Latin concernere "concern, touch, belong to," figurative use of Late Latin concernere "to sift, mix, as in a sieve," from Latin com- "with" (see com-) + cernere "to sift," hence "perceive, comprehend" (see crisis). Apparently the sense of the prefix shifted to intensive in Medieval Latin. Meaning "worry" is 17c. Related: Concerned; concerning. Letter opening to whom it may concern attested by 1740.
concern (n.): 1580s, from concern (v.).
concert (n.): 1660s, "agreement, accord, harmony," from French concert (16c.), from Italian concerto "concert, harmony," from concertare "bring into agreement," in Latin "to contend, contest, dispute," from com- "with" (see com-) + certare "to contend, strive," frequentative of certus, variant past participle of cernere "separate, decide" (see crisis).

Before the word entered English, meaning shifted from "to strive against" to "to strive alongside." Sense of "public musical performance" is 1680s. But Klein considers this too much of a stretch and suggests Latin concentare "to sing together" (from con- + cantare "to sing") as the source of the Italian word in the musical sense.
concertina (n.): 1835, from concert + fem. ending -ina. Portable musical instrument invented 1829 by Sir Charles Wheatstone. Concertina wire attested by 1917, so called from similarity to the musical instrument.
concerto (n.): 1730, from Italian concerto (see concert). Concerto grosso is from 1724.
concession (n.): mid-15c., from Old French concession (14c.) or directly from Latin concessionem (nominative concessio) "an allowing, conceding," noun of action from past participle stem of concedere (see concede). Meaning "right or privilege granted by government" is from 1650s. "Refreshment stand" sense is from 1910.
concessionaire (n.): 1862, from French concessionaire "person to whom a concession has been granted," from concession, from Latin concessionem (see concession).
conch (n.): type of shell, early 15c., from Latin concha "shellfish, mollusk," from Greek konkhe "mussel, shell," from PIE root *konkho-. The name for natives of Florida Keys since at least 1833; the preferred pronunciation there ("kongk") preserves the classical one.
concierge (n.): 1640s, from French concierge "caretaker, doorkeeper, porter" (12c.), probably from Vulgar Latin *conservius, from Latin conservus "fellow slave," from com- "with" (see com-) + servius "slave" (see serve (v.)).
conciliate (v.): 1540s, from Latin conciliatus, past participle of conciliare "to bring together, unite in feelings, make friendly," from concilium "council" (see council). Related: Conciliated; conciliating.
conciliation (n.): 1540s, from Middle French conciliation, from Latin conciliationem (nominative conciliatio) "a connection, union, bond," figuratively "a making friendly, gaining over," noun of action from past participle stem of conciliare (see conciliate).
conciliatory (adj.): 1570s, from conciliate + -ory. Related: Conciliator.
concise (adj.): 1580s, from Latin concisus "cut off, brief," past participle of concidere "to cut off, cut up, cut through, cut to pieces," from com-, intensive prefix (see com-), + caedere "to cut" (see -cide). Related: Concisely.
conciseness (n.): "expression of much in few words," 1650s, from concise + -ness.
[Conciseness] is the English word familiar to the ordinary man: concision is the LITERARY CRITIC'S WORD, more recent in English, used by writers under French influence & often requiring the reader to stop & think whether he knows its meaning. [Fowler]
concision (n.): late 14c., "cutting away, mutilation," also, from 16c., "circumcision," from Latin concisionem "a separation into divisions," literally "a cutting up," noun of action from past participle stem of concidere "to cut up" (see concise). From 18c. it began to be used in the sense of conciseness (q.v.).
conclave (n.): late 14c., "a place where cardinals meet to elect a pope," from Italian conclave, from Latin conclave "a room, chamber suite," probably originally "a room which may be locked," from com- "together" (see com-) + clavis "a key" (see slot (n.2)). Extended sense of "private assembly" is first recorded 1560s.
conclude (v.): early 14c., "end an argument," from Latin concludere "to shut up, enclose," from com- "together" (see com-) + -cludere, comb. form of claudere "to shut" (see close (v.)). Meaning "reach a mental conclusion, deduce" is from late 14c., a sense also in Latin. Related: Concluded; concluding.
conclusion (n.): late 14c., "deduction or conclusion reached by reasoning," from Old French conclusion "conclusion, result, outcome," from Latin conclusionem (nominative conclusio), noun of action from past participle stem of concludere (see conclude). Also, from late 14c. "the end" (usually of speech or writing), "closing passages of a speech or writing."