fly

{{11}}fly (adj.) slang, "clever, alert, wide awake," late 18c., perhaps from FLY (Cf. fly) (n.) on the notion of the insect being hard to catch. Other theories, however, trace it to fledge or flash. Slang use in 1990s might be a revival or a reinvention.

{{12}}fly (n.) O.E. fleoge "fly, winged insect," from P.Gmc. *fleugjon (Cf. O.S. fleiga, O.N. fluga, M.Du. vlieghe, Du. vlieg, O.H.G. flioga, Ger. Fliege "fly); lit. "the flying (insect)" (Cf. O.E. fleogende "flying"), from same source as fly (v.¹). Originally any winged insect (hence butterfly, etc.); long used by farmers and gardeners for any insect parasite. The O.E. plural in -n (Cf. oxen) gradually normalized 13c.-15c. to -s. Fly on the wall "unseen observer" first recorded 1881. An O.E. word for "curtain" was fleonet "fly-net." Fly-swatter first attested 1917. Fly-fishing is from 1650s.

{{12}}fly (v.¹) "to soar through air," O.E. fleogan "to fly" (class II strong verb; past tense fleag, pp. flogen), from W.Gmc. *fleuganan (Cf. O.S., O.H.G. fliogan, O.N. flügja, O.Fris. fliaga, M.Du. vlieghen, Du. vliegen, Ger. fliegen), from PIE *pleu- "flowing, floating" (see PLUVIAL (Cf. pluvial)). Notion of "flapping as a wing does" led to noun sense of "tent flap" (1810), which yielded (1844) "covering for buttons that close up a garment." The noun sense of "a flight, flying" is from mid-15c. Baseball fly ball attested by 1866. Slang phrase fly off the handle "lose one's cool" dates from 1825. To do something on the fly is 1856, apparently from baseball.

{{13}}fly (v.²) "run away," O.E. fleon (see FLEE (Cf. flee)). Fleogan and fleon were often confused in O.E., too. Mod.Eng. distinguishes in preterite: flew/fled.