late 14c., "to make oneself trim or smart," perhaps from Old North French perquer "to perch" (Modern French percher; see perch (n.1)), on notion of a bird preening its plumage. Sense of "raise oneself briskly" is first attested 1520s; perk up "recover liveliness" is from 1650s. Related: Perked; perking.
perk (n.)
1869, shortened and altered form of perquisite (q.v.); as a verb, 1934 as shortened and altered form of percolate.
