1703, "union of parts, parts of a thing taken together," from French ensemblée "all the parts of a thing considered together," from Late Latin insimul "at the same time," from in- intensive prefix + simul "at the same time," related to similis "like, resembling, of the same kind" (see similar). Musical sense of "union of all parts in a performance" in English first attested 1844. Of women's dress and accessories, from 1927. Earlier in English as an adverb (mid-15c.), "together, at the same time."