1590s, earlier grine (1530s), from Middle English grynde "groin" (c.1400), originally "depression in the ground," from Old English grynde "abyss," perhaps also "depression, hollow," from Proto-Germanic *grundus (see ground). Altered 16c. by influence of loin or obsolete groin "snout." The architectural groin "edge formed by the intersection of two vaults" is from 1725.