early 14c., transitive ("collect into one place") and intransitive ("meet or come together"), from Old French assembler "come together, join, unite; gather" (11c.), from Latin assimulare "to make like, liken, compare; copy, imitate; feign, pretend," later "to gather together," from assimilated form of ad "to" (see ad-) + simulare "to make like," from stem of similis "like, resembling, of the same kind" (see similar). In Middle English and in Old French it also was a euphemism for "to couple sexually." Meaning "to put parts together" in manufacturing is from 1852. Related: Assembled; assembling. Assemble together is redundant.