From dictionary.com:
Wry- Dryly humorous, often with a touch of irony.
Cooter- A freshwater tortois of Florida. (Or a town in MO).
So unless cooter has some slang meaning, "Wry Cooter" is a dryly humorous turtle from Florida. God I love dictionary.com...
(Though I'm sure the Wry Cooter can fill us in on the real reason he called himself that. Cool name!)
Matthew