Nicknames:
Theo, Eon.
Famous people named Theon:
Greek philosopher Theon of Smyrna; Greek painter Theon of Samos.
Fun fact:
Theon Greyjoy is a character in George R.R. Martin's Game of Thrones series.
Derived from a Greek word meaning "of the gods." And your little Theon will definitely be such a gift, although you may wonder during tantrums sometimes if he came from somewhere a little more ... southern.