1650s, "compounded a second time, compounded from things already composite," from Late Latin compositus, in grammar (rendering Greek parasynthetos), "formed from a compound," literally "placed together," past participle of componere "to put together, to collect a whole from several parts," from com "with, together" (see com-) + ponere "to place" (past participle positus; see position (n.)). Earlier in English as a noun, "something compounded of composite things" (1620s). Middle English had decompound (adj.) in grammar (mid-15c.).
