Why are Portuguese water dogs called dogs?

Portuguese Water Dogs are called "dogs" because they are, in fact, dogs.

The word "dog" is a general term used to describe canines, which are members of the Canidae family. Portuguese Water Dogs belong to this family, just like Golden Retrievers, Poodles, and many other breeds.

The reason they are called "Portuguese Water Dogs" is because of their origin (Portugal) and their historical use as working dogs in the water, assisting fishermen.