early 15c., "to associate, unite, join two or more things together" (transitive), from Old French combiner (14c.) and directly from Late Latin combinare "to unite, yoke together," from Latin com "with, together" (see com-) + bini "two by two," adverb from bi- "twice" (from PIE root *dwo- "two"). Intransitive sense "unite, coalesce, come together into one body" is from 1712. Related: Combinative; combined; combining.