William
William was a common Human given name.
In 2368, after Miles O'Brien and Keiko discussed naming their baby after their fathers, William T. Riker suggested the name "William". He thought "William O'Brien" had a nice ring to it. (TNG: "Disaster")
One of the shortened familiar versions of this name – "Bill" – was used by Deanna Troi when she was getting William Riker's attention in the "The Naked Now", and twice in "Haven". For the rest of the series and into the films, William Riker was known by another shortened familiar version: "Will".