What is the X in X-mas?
Old English strica "line of motion, stroke of a pen" (related to strican "pass over lightly," see strike), from Proto-Germanic *strikon (cf. Middle Low German streke "stroke, line," Old High German, German strich, Gothic striks "stroke, line"), from PIE root *streig- (see strigil). Sense of "long, thin mark" is first found 1567. Meaning "a temporary run (of luck)" is from 1843.
A line, stripe, smear, or band differentiated by color or texture from its surroundings.
[1894+; said to be fr the arrangement of a threshing crew, where the chief would superintend the grain itself, and the second the straw; perhaps fr Dutch stroodekkerbaas]