1590s, transitive, "to form into a ball, to gather into a ball or round body," from Latin conglomeratus, past participle of conglomerare "to roll together, concentrate, heap up," from assimilated form of com "with, together" (see con-) + glomerare "to gather into a ball, collect," from glomus (genitive glomeris) "a ball, ball-shaped mass," possibly from PIE *glem- (see glebe). Intransitive sense of "to come together in a rounded mass" is from 1640s. Related: Conglomerated; conglomerating.