Английский Этимологический словарь - fly (v1.)

- "to soar through air," O.E. fleogan (class II strong verb; past tense fleag, pp. flogen), from W.Gmc. *fleuganan, from PIE *pleu- "flowing, floating." Notion of "flapping as a wing does" led to sense of "tent flap" (1810), which yielded (1844) "covering for buttons that close up a garment." The slang sense (n. and adj.) "wide awake" is 18c., perhaps from fledge. Flyer "small handbill or fly-sheet" is 1889, U.S. slang, from notion of "made to be scattered broadcast." Flying saucer first attested 1947, though the image of saucers for unidentified flying objects is from at least 1880s. Fly-by-night was said to be an old term of reproach to a woman, signifying that she was a witch; extended early 19c. to anyone who departs hastily from a recent activity. Slang phrase fly off the handle "lose one's cool" dates from 1825. Flying colors (1706) is probably from the image of a naval vessel with the national flag bravely displayed. Flying fuck originally meant "have sex on horseback" and is first attested c.1800 in broadside ballad "New Feats of Horsemanship."