Cassius is lovely. Someone mentioned it's meaning would be hard to stomach so I googled it: 'helmet' or 'vessel', or possibly, from another etymological angle, 'empty' or 'vain'. Honestly, I can think of worse meanings.
Otherwise, Thaddeus is a great name, meaning 'courageous heart'. I think it has a Cassius kind of vibe but a much more potent meaning.