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 "part," from Latin pars (see part (n.)) in 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.