Or is it hotdog?
A hot dog — or hotdog — is a sandwich made with a wiener (a sausage)…skinless or otherwise. The wiener is not a hot dog/hotdog; by itself it is just a wiener.
The hot dog/hotdog doesn't happen until it becomes a sandwich. Condiments (ketchup, mustard, relish, onions) are optional. But the bun is essential.