I know Fia is used a lot as a nickname. I could see how it would be perceived as childish. I've come to a point where it doesn't really bother me.
And wow. I'd have never know of the vulvular association with Fia. I'm not sure how I feel about that. I mean,
Iona means vagina in Samoan. I still like the name though. Hm. It's definitely something to think about.
Thank you!
http://www.babynames.com/namelist/9852886