thrash (v.) Look up thrash at Dictionary.com
1580s, "to separate grains from wheat, etc., by beating," dialectal variant of threshen (see thresh). Sense of "beat (someone) with (or as if with) a flail" is first recorded 1620s. Meaning "to make wild movements like those of a flail or whip" is attested from 1846. Related: Thrashed; thrashing. As a noun from 1660s, "threshing tool;" 1840s as "a beating;" 1982 as the name for a type of fast heavy metal music.