Origin and history of fatuous

1640s, from French fatuité (14c.), from Latin fatuitatem (nominative fatuitas) "foolishness, folly," from fatuus "foolish, insipid" (see fatuous).

"fairy," late 14c., from Old French fae, feie (12c., Modern French fée) from Medieval Latin fada. OED derives it from Latin Fata, "the Fates" (see fate) ultimately from fatum, neuter past participle of fari "to speak." However Fata is a rare word in Latin (the Fates were usually referred to as the Parcae), and another possibility is that it is a derivative of Fatuus as an alternative name for the Roman oracular god Faunus (see fatuous), who resembled northern European mythic figures such as the woodwose, and whose name may have become a term for one who was psychic or insane (as suggested by de Vaan). Fatua is a term used by Arnobius Afer (4c.) to describe similar pagan entities. Compare also Odin.

[By the 1450s] The French word derived ultimately from the fays of chivalric romance had become thoroughly naturalized among the English and freighted with a set of royal associations not given before to the native 'elves' whom it had largely replaced. [Ronald Hutton, Queens of the Wild, 2022.]

Middle English also used fay as an adjective to mean "enchanted, magical" (late 14c.). The modern adjective meaning "homosexual" is attested by 1950s. For the "white person" sense see ofay.