its a Roman nickname, but agnomen works.
Hecate
Ike
ron
Wart
Wart
God is not your home-boy. There is no nickname for Him. Plus, I don't know why you want a nickname. I mean 'God' is a three letter word!
Iraq Shaq, nickname for Shaquille.
Perhaps penname? Hope this helps.
bard
Jock is a nickname for a Scotsman. ***** A native of Scotland is a Scot.
"Tommy" is not an Irish word.