in two shakes

Also, in two shakes of a lamb’s tail Very quickly, very soon, as in I’ll be with you in two shakes, or She’ll be finished in two shakes of a lamb’s tail. The longer idiom alludes to the friskiness of lambs; the shorter one may be an abbreviation of the longer one, or it may refer to the shaking of dice or any two quick movements. [Early 1800s]