What is the X in X-mas?
Old English bitan (class I strong verb; past tense bat, past participle biten), from Proto-Germanic *bitan (cf. Old Saxon bitan, Old Norse and Old Frisian bita, Middle Dutch biten, Dutch bijten, German beissen, Gothic beitan "to bite"), from PIE root *bheid- "to split, crack" (see fissure).
To bite the bullet is said to be 1700s military slang, from old medical custom of having the patient bite a lead bullet during an operation to divert attention from pain and reduce screaming. Figurative use from 1891; the custom itself attested from 1840s. To bite (one's) tongue "refrain from speaking" is 1590s. To bite the dust "die" is 1750 (Latin had the same image; cf. Virgil: procubuit moriens et humum semel ore momordit). To bite off more than one can chew (c.1880) is U.S. slang, from plug tobacco.
c.1200, from bite (v).
v. bit (bĭt), bit·ten (bĭt'n) or bit, bit·ing, bites
To cut, grip, or tear with the teeth.
To pierce the skin of with the teeth, fangs, or mouthparts.
The act of biting.
A puncture or laceration of the skin by the teeth of an animal or the mouthparts of an insect or similar organism.