What is the X in X-mas?
mid-15c., probably from Middle English icchen "to move as with a jerk, to stir" (c.1200). It lacks cognates in other languages. The connection with icchen may be in notion of "hitching up" pants or boots with a jerking motion. Sense of "become fastened," especially by a hook, first recorded 1570s, originally nautical. Meaning "to marry" is from 1844 (to hitch horses together "get along well," especially of married couples, is from 1837, American English). Short for hitchhike (v.) by 1931. Related: Hitched; hitching.
1660s, "a limp or hobble;" 1670s, "an abrupt movement," from hitch (v.). Meaning "a means by which a rope is made fast" is from 1769, nautical. The sense of "obstruction" is first recorded 1748; military sense of "enlistment" is from 1835.