piecemeal (adv.)
c.1300 (originally two words), from piece (n.) + Old English mælum "at a time," dative plural of mæl "appointed time, food served" (see meal (n.1)). The second element once was more commonly used, as in Old English styccemælum "bit by bit," gearmælum "year by year." One-word form from 15c.