c. 1300, "to dash, run, rush," probably from or related to Old Norse flengja "to flog," which is of uncertain origin, perhaps from Proto-Germanic *flang- (source also of Old Swedish flenga "strike," Danish flænge "slash, gash"), from a nasalized variant of PIE root *plak- (2) "to strike." Meaning "to throw, cast, hurl" is from mid-14c. An obsolete word for "streetwalker, harlot" was fling-stink (1670s). Related: Flung; flinging, but in Middle English with past tense flang, past participle flungen.