What is the X in X-mas?
Old English wecg "a wedge," from Proto-Germanic *wagjaz (cf. Old Norse veggr, Middle Dutch wegge, Dutch wig, Old High German weggi "wedge," German Weck "wedge-shaped bread roll"), of unknown origin. Wedge issue is attested from 1999.
mid-15c., from wedge (n.). Related: Wedged; wedging.