1560s, alteration of older garsh, from Middle English garsen (late 14c.), from Old North French garser "to cut, slash" (see gash, n.). For loss of -r-, see ass, n.2. Related: Gashed; gashing.

1540s, alteration of Middle English garce "a gash, cut, wound, incision" (early 13c.), from Old North French garser "to scarify, cut, slash" (Old French *garse), apparently from Vulgar Latin *charassare, from Greek kharassein "engrave, sharpen, carve, cut," from PIE *gher- (4) "to scrape, scratch" (see character). Loss of -r- is characteristic (see ass, n.2). Slang use for "vulva" dates to mid-1700s. Provincial English has a set of words (gashly, gashful, etc.) with forms from gash but senses from gast- "dreadful, frightful."