There's no turkey in this dish! Cape Cod Turkey is a classic 18th-19th Century New England fish dish made with fresh or salt cod and dressed with white sauce and hard-boiled egg. It's a close relative of the smokey Finnan Haddie.
The version described here is made with salt cod, which would have been common in most of New England more than a short distance from the coast. Salt Cod, even after it's been freshened, has a denser, meatier texture than fresh cod.