early 14c., "protuberance on the body, swelling," perhaps echoic of the sound of hitting and connected to bump (cf., possibly, hump/hunch). As a verb meaning "to bulge out," from late 14c. The noun sense of "cluster" is mid-15c.; connection with the earlier sense is obscure, and this may be a separate word, perhaps through O.Fr. bouge (2), 15c., from Flemish boudje dim. of boud "bundle." The verb meaning "to gather up in a bunch" (trans.) is from 1828; that of "to crowd together" (intrans.) is from 1873. Related: Bunched; bunching.