The name Hart is a boy's name of English origin meaning "stag". Hart and is often added to lists like Best Cool Unusual Boys' Names and discussed in our forums with posts like "What would you name a sibling to...?".
From the experts:
Hart could be the hero of a romantic novel, but on the other hand, it's short, straightforward, and strong sounding. The most famous bearer of the name was tragic poet Hart (born Harold) Crane, but it also has musical cred via Lorenz Hart, of the classic Rodgers & Hart songwriting duo and a literary tie to playwright Moss Hart.
Hart would make an interesting middle name choice--with heart.