What is the X in X-mas?
Old English sceaf (plural sceafas) "large bundle of corn," from Proto-Germanic *skauf- (cf. Old Saxon scof, Middle Dutch scoof, Dutch schoof, Old High German scoub "sheaf, bundle," German Schaub "sheaf;" Old Norse skauf "fox's tail;" Gothic skuft "hair on the head," German Schopf "tuft"), from PIE root *(s)keup- "cluster, tuft, hair of the head." Extended to bundles of things other than grain by c.1300. Also used in Middle English for "two dozen arrows." General sense of "a collection" is from 1728.