The name Sam is a girl's name of Hebrew origin meaning "told by God". Sam and is often added to lists like Middle Names for Girls and discussed in our forums with posts like "Love, Like, Lose -- Outlandish/Guilty Pleasures edition!".
From the experts:
Sam as a name standing on its own was given to only 12 girls in 2015, versus over 500 boys. But as a short form it's appealing and down-to-earth for both sexes, and heard far more often: There were over 5000 baby girls named Samantha in the US in one recent year and more than 10,000 boys named Samuel, so you will hear the name Sam a lot more often than you might guess judging by the numbers for this short form. Like Charlie, Sam is a nickname that works equally well as a girls' name as a boys'.