harum-scarum (adv.)

"to harry, harass," 1520s; meaning "to frighten" is 1650s; of uncertain origin; connections have been suggested to harry (v.) and to hare (n.). Related: Hared; haring.

1590s, "frighten, terrify suddenly," an unusual alteration of Middle English skerren "to frighten" someone (late 12c.), from Old Norse skirra "to frighten; to shrink from, shun; to prevent, avert," which is related to skjarr "timid, shy, afraid of," but of unknown origin.

In Scottish also skair, skar, which seem to track closer to the word's expected development, and in dialect skeer, skear. Intransitive meaning "become frightened, be scared" is from 14c.; the specific sense of "be alarmed by rumor" is from 1900.

To scare away "drive off by frightening" is from 1650s. To scare up "procure, obtain, find, bring to light" is recorded by 1846, American English, from notion of rousing game from cover. Related: Scared; scaring.