beat it

c.1300, "a beating, whipping; the beating of a drum," from beat (v.). As "throb of the heart" from 1755. Meaning "regular route travelled by someone" is attested from 1731, also "a track made by animals" (1736), from the sense of the "beat" of the feet on the ground (late Old English), or perhaps that in beat the bushes to flush game (c.1400), or beat the bounds (1560s). Extended to journalism by 1875. Musical sense is by 1842, perhaps from the motion of the conductor and the notion of "beating the time":

Earlier in music it meant a sort of grace note: