What is the X in X-mas?
early 15c., "meat or fish market," from schamil "table, stall for vending" (c.1300), from Old English scamol, scomul "stool, footstool (also figurative); bench, table for vending," an early West Germanic borrowing (cf. Old Saxon skamel "stool," Middle Dutch schamel, Old High German scamel, German schemel, Danish skammel "footstool") from Latin scamillus "low stool, a little bench," ultimately a diminutive of scamnum "stool, bench," from PIE root *skabh- "to prop up, support." In English, sense evolved from "place where meat is sold" to "slaughterhouse" (1540s), then figuratively "place of butchery" (1590s), and generally "confusion, mess" (1901, usually in plural).
"to walk with a shuffling gait, walk awkwardly and unsteadily," 1680s, from an adjective meaning "ungainly, awkward" (c.1600), from shamble (n.) "table, bench" (see shambles), perhaps on the notion of the splayed legs of bench, or the way a worker sits astride it. Cf. French bancal "bow-legged, wobbly" (of furniture), properly "bench-legged," from banc "bench." The noun meaning "a shambling gait" is from 1828. Related: Shambled; shambling.