Turns out he tried to escape down the overflow from the tub. Didn't work out for him, in the short term. In the long term, though, it's much better for him. He's doing time in a big plastic trash can until we find a better habitat. Going to grow the basement dragon up big and strong before we turn him loose to eat the mice.
We agreed on "Ratbane," from the names you recommended. I liked several of the entries, but I'm not the only vote around here.