Interesting, that Swedish forms the same "boyfriend" and, presumably, girlfriend. I wonder where it originates?
I had a poke around; not clear to me but it’s a relatively modern formation in both languages, especially in the romantic sense which developed later than the platonic sense. Some other northern European languages (including the non-Germanic Finnish) have similar compounds or at least gendered “friend” type words. The most likely explanation is that one or more directly influenced the others. English term seems to originate a bit earlier than Swedish term, at least for boyfriend.