What is the X in X-mas?
Old English hoc "hook, angle," perhaps related to Old English haca "bolt," from Proto-Germanic *hokaz/*hakan- (cf. Old Frisian hok, Middle Dutch hoek, Dutch haak, German Haken "hook"), from PIE *keg- "hook, tooth" (cf. Russian kogot "claw"). For spelling, see hood (n.1).
Boxing sense of "short, swinging blow with the elbow bent" is from 1898. Figurative sense was in Middle English (see hooker). By hook or by crook (late 14c.) probably alludes to tools of professional thieves. Hook, line, and sinker "completely" is 1838, a metaphor from angling.
(1.) Heb. hah, a "ring" inserted in the nostrils of animals to which a cord was fastened for the purpose of restraining them (2 Kings 19:28; Isa. 37:28, 29; Ezek. 29:4; 38:4). "The Orientals make use of this contrivance for curbing their work-beasts...When a beast becomes unruly they have only to draw the cord on one side, which, by stopping his breath, punishes him so effectually that after a few repetitions he fails not to become quite tractable whenever he begins to feel it" (Michaelis). So God's agents are never beyond his control. (2.) Hakkah, a fish "hook" (Job 41:2, Heb. Text, 40:25; Isa. 19:8; Hab. 1:15). (3.) Vav, a "peg" on which the curtains of the tabernacle were hung (Ex. 26:32). (4.) Tsinnah, a fish-hooks (Amos 4:2). (5.) Mazleg, flesh-hooks (1 Sam. 2:13, 14), a kind of fork with three teeth for turning the sacrifices on the fire, etc. (6.) Mazmeroth, pruning-hooks (Isa. 2:4; Joel 3:10). (7.) 'Agmon (Job 41:2, Heb. Text 40:26), incorrectly rendered in the Authorized Version. Properly a rush-rope for binding animals, as in Revised Version margin.