grate (n.) Look up grate at Dictionary.com
c.1400, from M.L. grata "lattice," from L. cratis "wickerwork."
grate (v.) Look up grate at Dictionary.com
1390 (implied in grater), from O.Fr. grater "to scrape," from Frank. *kratton, from P.Gmc. *krattojan (cf. O.H.G. krazzon "to scratch, scrape"), probably of imitative origin. Senses of "sound harshly," and "annoy" are 16c.