If his name isn't Lou Tenant, it's obviously Costello (no surname).
Or maybe it's something that can't be spoken by mortal tongues.
"I AM COSTELLO, AN ANGEL (and a pretty kickass one if I may as so myself. I'm also French!)"
"Right, and what's your real name?"
"I, uh, can't tell you."
"Why?"
"If you try to repeat it, your tongue will twist so tightly that it'll form a black hole that will destroy all of creation."
"....that sounds pretty cool actually. So what's your real name?"
Or maybe it's something that can't be spoken by mortal tongues.
"I AM COSTELLO, AN ANGEL (and a pretty kickass one if I may as so myself. I'm also French!)"
"Right, and what's your real name?"
"I, uh, can't tell you."
"Why?"
"If you try to repeat it, your tongue will twist so tightly that it'll form a black hole that will destroy all of creation."
"....that sounds pretty cool actually. So what's your real name?"