Groin
late Middle English grynde, perhaps from Old English grynde ‘depression, abyss’.
wiktionary
From earlier grine, from Middle English grinde, grynde, from Old English grynde(“abyss”) (perhaps also "depression, hollow"), probably related to Proto-Germanic *grunduz; see ground. Later altered under the influence of loin.
From Middle English groynen, from a mixture of Old French groignier, grougnier (from Latin grunniō) and Old English grunnian (from Proto-Germanic *grunnōną).
groin (plural groins)
etymonline
groin (n.)
"oblique depression of the body between the abdomen and thighs," 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 (n.)). Altered 16c. by influence of loin or obsolete groin "snout of a pig." The architectural groin "curving edge formed by the intersection of two vaults" is from 1725.
