means The act of leaving the ground to begin flight, or more broadly the moment something launches, departs, or surges upward.

from A plain compound of "take" and "off," both old Germanic-rooted English words. The literal sense of "taking off" — lifting or removing something — is centuries old, but the aviation meaning is young, arriving with powered flight in the early 20th century: the airplane "takes off" from the runway the way a hat is taken off a head. The mimicry sense (a "takeoff" of someone, an imitation) comes from the older idea of "taking off" a person's likeness or manner.