"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.
"humorous," 1756, from fun (n.) + -y (2). Meaning "strange, odd, causing perplexity" is by 1806, said to be originally U.S. Southern (marked as colloquial in Century Dictionary). The two senses of the word led to the retort question "funny ha-ha or funny peculiar," which is attested by 1916. Related: Funnier; funniest. Funny farm "mental hospital" is slang from 1962. Funny bone "elbow end of the humerus" (where the ulnar nerve passes relatively unprotected) is from 1826, so called for the tingling sensation when struck. Funny-man was originally (1854) a circus or stage clown.
"A fly ball hit to a player during fielding practice in which the batter (often a coach) tosses the ball into the air and hits it as it descends with a long and narrow bat." [Paul Dickson, "The Dickson Baseball Dictionary," 3rd ed., 2009], attested from 1867 (fungoes), baseball slang, of unknown origin; see Dickson's book for a listing of the guesses. Perhaps from a Scottish fung "to pitch, toss, fling;" perhaps from some dialectal fonge "catch," a relic of Old English fon "seize" (see fang), or possibly from the German cognate fangen. Not in OED 2nd ed. (1989). There does not seem to have been a noun phrase (a) fun go in use at the time. It formally resembles the Spanish and Italian words for "fungus."
"make fun of, tease in a good-natured way, attack with raillery," 1660s, from French railler "to rail, reproach" (see rail (v.1)).