- frail (adj.)
- mid-14c., "morally weak," from Old French fraile, frele "weak, frail, sickly, infirm" (12c., Modern French frêle), from Latin fragilis "easily broken" (see fragility). It is the Frenchified form of fragile. Sense of "easily destroyed, liable to break" in English is from late 14c. The U.S. slang noun meaning "a woman" is attested from 1908; perhaps with awareness of Shakespeare's "Frailty, thy name is woman."
- imbecile (adj.)
- 1540s, imbecille "weak, feeble" (especially in reference to the body), from Middle French imbecile "weak, feeble" (15c.), from Latin imbecillus "weak, feeble" (see imbecility). Sense shifted to mental weakness or incapacity from mid-18c. (compare frail, which in provincial English also could mean "mentally weak"). As a noun, "feeble-minded person," it is attested from 1802. Traditionally an adult with a mental age of roughly 6 to 9 (above an idiot but beneath a moron).
- frailty (n.)
- mid-14c., freylte, from Old French fraileté "frailty, weakness," from Latin fragilitatem (nominative fragilitas) "weakness, frailty," from fragilis "fragile" (see fragility). Related: Frailties.
- infirmary (n.)
- mid-15c., "sick bay in a monastery," formerly also enfermerie, also firmary, fermery, from Old French enfermerie "hospital" and directly from Medieval Latin infirmaria "a place for the infirm," from Latin infirmus "weak, frail," (see infirm). According to OED, the common name for a public hospital in 18c. England.
- fragile (adj.)
- 1510s, "liable to sin, morally weak;" c. 1600, "liable to break;" a back-formation from fragility, or else from Middle French fragile (Old French fragele, 14c.), from Latin fragilis "easily broken," from root of frangere "to break" (see fraction). Transferred sense of "of frail constitution" (of persons) is from 1858.
- 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."
- gerontology (n.)
- 1903, coined in English from geronto-, used as comb. form of Greek geron (genitive gerontos) "old man," from PIE root *gere- "to become ripe, grow old" (source also of Sanskrit jara "old age," jarati "makes frail, causes to age;" Avestan zaurvan "old age;" Ossetic zarond "old man;" Armenian cer "old, old man").
- infirm (adj.)
- late 14c., "weak, unsound" (of things), from Latin infirmus "weak, frail, feeble, not strong or firm" (figuratively "superstitious, pusillanimous, inconstant"), from in- "not, opposite of" (see in- (1)) + firmus "strong; stable," figuratively "constant, trusty" (see firm (adj.)). Of persons, "not strong, unhealthy," first recorded c. 1600. As a noun from 1711.
