Officially, this is a masculine name. It's not common, so I wouldn't be surprised to hear it used as a girl's nickname, but I'd expect it to be hard to pass it officially as a girl's name, since, according to the statistics from the Finnish Population Register Centre, it's always been exclusively masculine.
This is really not a masculine name, but a nickname for a girl named Vilhelmiina, Vilma or other names beginning with "Vil" or "Wil" (just like slight night shiver said).
― Anonymous User 6/27/2009
1
Mwahahaha, I thought this name was feminine! It sounds like a nickname for a little girl. I've never heard of anyone named Vilppu anyway.