English word unseen comes from Proto-Germanic *unsewanaz

Detailed word origin of unseen

Dictionary entry	Language	Definition
*unsewanaz	Proto-Germanic (gem-pro)
unġesewen	Old English (ang)
unseien	Middle English (enm)
unseen	English (eng)	(obsolete) Not hitherto noticed; unobserved.. Not seen or discovered; invisible.. Unskilled; inexperienced.