1550s, "to state the parts of speech in a sentence," verb use of Middle English pars (n.) "part of speech" (c. 1300), from Old French pars, plural of part "a part," from Latin pars "a part, piece" (from PIE root *pere- (2) "to grant, allot") in the school question, Quae pars orationis? "What part of speech?" Transferred (non-grammatical) use is from 1788. Pars was a common plural of part (n.) in early Middle English. Related: Parsed; parsing.