Where does “Danmǫrk” come from?

Danmǫrk (Old Norse) comes from Old Norse mǫrk, from Proto-Germanic markō, from Proto-Indo-European morǵ- — edge, boundary, border; frontier, border.

Ancestry of “Danmǫrk”, step by step

Step	Language	Word	Meaning
1	Old Norse	mǫrk	mark, by weight or value, = eight ounces; forest
2	Proto-Germanic	markō	border, boundary; region, area
3	Proto-Indo-European	morǵ-	edge, boundary, border; frontier, border

Danmǫrk — Etymology, Origin & Word History | Etymology Explorer