Ipso facto:
Bill = Billiam
Mutatis Mutandis:
Jim = Jimothy
Only issue I recall might be with female Aleksandra (abbreviated to Ola) and male Aleksander (abbreviated to Olo, or Olek).
Others usually (if I remember correctly) have similar prefix.
Wow, is this one common?
The author Jack London was originally John London. John F. Kennedy was familiarly known as Jack ("Senator, you're no Jack Kennedy"). The British racing driver John Stewart is far more commonly known as Jackie Stewart. In Patrick O'Brian's naval fiction, Captain John Aubrey is almost always referred to as Jack.
Hahya Ivan Giovanni Shawn
Although if we’re talking Hebrew > Greek > European borrowings I’m guessing Chava = Eve is funnier. For bonus funny points, ave (as in Ave Maria or Ave, imperator) comes from essentially the same Hebrew word as well.