What is the X in X-mas?
mid-14c. (mid-13c. in Anglo-Latin), "to take or seize (property or goods) by law," a legal term, from Old French atachier (11c.), earlier estachier "to attach, fix; stake up, support" (Modern French attacher, also cf. Italian attaccare), perhaps from a- "to" + Frankish *stakon "a post, stake" or a similar Germanic word (see stake (n.)). Meaning "to fasten, affix, connect" is from c.1400. Related: Attached; attaching.