Fun
late 17th century (denoting a trick or hoax): from obsolete fun ‘to cheat or hoax’, dialect variant of late Middle English fon ‘make a fool of, be a fool’, related to fon ‘a fool’, of unknown origin. Compare with fond.
wiktionary
From Middle English fonne, fon(“foolish, simple, silly”) or fonnen(“make a fool of”), probably of North Germanic origin, related to Swedish fånig(“foolish”), Swedish fåne(“a fool”). Compare also Norwegian fomme, fume(“a fool”). More at fon, fond.
As a noun, fun is recorded from 1700, with a meaning “a cheat, trick, hoax”, from a verb fun meaning “to cheat, trick” (1680s). The meaning “diversion, amusement” dates to the 1720s. The older meaning is preserved in the phrase to make fun of (1737) and in usage of the adjective funny. The use of fun as adjective is newest and is due to reanalysis of the noun; this was incipient in the mid-19th century.
Alternative etymology connected Middle English fonne with Old Frisian fonna, fone, fomne, variant forms of fāmne, fēmne(“young woman, virgin”), from Proto-West Germanic *faimnijā, from Proto-Germanic *faimnijǭ(“maiden”), from Proto-Indo-European *peymen-(“girl”), *poymen-(“breast milk”). If so, then cognate with Old English fǣmne(“maid, virgin, damsel, bride”), West Frisian famke(“girl”), Saterland Frisian fone, fon(“woman, maid, servant," also "weakling, simpleton”).
etymonline
fun (n.)
"diversion, amusement, mirthful sport," 1727, earlier "a cheat, trick" (c. 1700), from verb fun (1680s) "to cheat, hoax," which is of uncertain origin, probably a variant of Middle English fonnen "befool" (c. 1400; see fond). Scantly recorded in 18c. and stigmatized by Johnson as "a low cant word." Older senses are preserved in phrase to make fun of (1737) and funny money "counterfeit bills" (1938, though this use of the word may be more for the sake of the rhyme). See also funny. Fun and games "mirthful carryings-on" is from 1906.
fun (v.)
1680s, "to cheat;" 1833 "to make fun, jest, joke," from fun (n.). Related: Funning.
fun (adj.)
mid-15c., "foolish, silly;" 1846, "enjoyable," from fun (n.).
