Word Origin & History
grinO.E. grennian "show the teeth" (in pain or anger), common Gmc. (cf. O.N. grenja "to howl," grina "to grin;" Du. grienen "to whine;" Ger. greinen "to cry"), from PIE base *ghrei- "be open." Sense of "bare the teeth in a broad smile" is c.1480, perhaps via the notion of "forced or unnatural smile." the
noun is first attested 1635.