flare (v.)youdaoicibaDictYouDict[flare 词源字典]
1540s, "spread out" (hair), of unknown origin, perhaps from Scandinavian or from Dutch vlederen. Meaning "shine out with a sudden light" is from 1630s. The notion of "spreading out in display" is behind the notion of "spreading gradually outward" (1640s). Related: Flared; flaring.[flare etymology, flare origin, 英语词源]