depends on the kind of magic. the sort you are thinking of is seidhr, which were considered feminine for a few reasons: one it was a vanic magic, taught by freya to odin originally. odin practiced it once, during which he entered a 3 day trance where his body laid still and his spirit roamed the 9 worlds, and after that he declared it was forbidden for men to do it since it unmanned them. it unmanned them not in the sense of making them gay or whatever but in the sense that it made them weak and helpless for 3 days, which isnt something a man should be doing. its like how psychdelics are cool and all, but you turn into a faggot really quick if youre doing acid every day and not taking care of IRL business like a man should.

there were other types of magic not associated with women, or any particular gender. rune magic for example seems to have been exclusively a male thing; female names are very rarely carved unto runestones as the names of those who raised the stone, and never as the name of the carver. we also have the curious phenomena of the nordic witch hunts, which primarily targeted men over women in contrast to the witch hunts of the rest of europe. in iceland over 90 percent of convicted witches were men, which seems to contrast with the idea that magic was considered womans work in nordic culture, or that the form of magic being practiced in scandinavia at the time was not like seidhr or the forms of witchcraft in europe. the galdrbok, the only known icelandic grimoire, is clearly targeted for male magic practitioners, and contains few spells that would aid a woman. there are spells for seducing women with charms, but none for the opposite, which is why i believe its a mans grimoire and not a womans