Old English granian "to utter a deep, low-toned breath expressive of grief or pain; to murmur; to lament," from Proto-Germanic *grain- (source also of Old Norse grenja "to howl"), of imitative origin, or related to grin (v.). Meaning "complain" is from early 13c., especially in Middle English phrase grutchen and gronen. As an expression of disapproval, by 1799. Related: Groaned; groaning.
late 14c., from groan (v.); earlier grane (early 14c.).