The name Tommy is a boy's name meaning "twin". Tommy is ranked #709 on our popularity charts and is often added to user-created lists like Punk Rock Names for Cool Kids and discussed in our forums with posts like "A brother or sister for little Jack or Olivia".
From the experts:
A surprising number of parents choose to put the nickname Tommy on their son's birth certificate rather than the more traditional Thomas. Perhaps even more surprising is that fact that Tommy has never been off the United States popularity charts. More recently, however, the name has been trending downward.