Hacker News Reader

It's very unusual for girls, probably because it literally means "male"

No, it is from French: literally, "handsome," or the masculine form of "beautiful." Still an odd choice for a girl. The definition you quote is what it has come to mean in English, but it is really a shorthand.

Technically, the girls named "Beau" should have been named "Belle".

Yet even more unusual than Adam for girls.

1 in 220,489 girls (http://www.babynamescience.com/baby-name/Adam-girl)

Not so much so in the UK though, where she lives. 198 girls born in 2015 with the name putting it at #249 (more popular than Mary, Kate, Diana or Michelle - all top 10 names at one point in the past).

Source: http://www.ons.gov.uk/peoplepopulationandcommunity/birthsdea...