also back-biting, c. 1200, bacbitunge, "the sin of secretly attacking one's character or reputation through envy," from back (adj. or n.) + verbal noun from bite (v.). The notion is of injury in a manner comparable to biting from behind. As an adjective Old English had bæcslitol; another old word for it was back-wounding (c. 1600). Related: back-bite (v.) early 14c.; back-biter (c. 1200).

mid-13c., "long, straight, narrow cut or rent (in clothes); narrow opening, incision," from slit (v.). Slang sense of "vulva" is attested from 1640s. Old English had slit (n.) with a sense of "a rending, bite; backbiting."