An important definition to keep in mind is that a lie is any intention to deceive. Sometimes it helps to keep this in mind, especially if we start to soften our attitude toward the scammer.
Why the term “Catfish?” Urban legend says that catfish were put in shipping containers that held cod, for various reasons. It seems that may not be true, which would make “catfish” a great metaphor for a story that doesn’t make sense and isn’t true anyway. But my favorite definition for the term is that of predatory bottom-feeder, which pretty much describes scammers/catfish.