What is the X in X-mas?
Old English norþerna, norðerne "northern, Northumbrian, Scandinavian," cognate with Old High German nordroni, Old Norse norroenn (see north). With -erne, suffix denoting direction. Related: Northernmost. Northerner in U.S. geo-political sense is attested from 1831. Northern lights "aurora borealis" first recorded by that name 1721 (earlier north-light, 1706).