"Joe momma" is called that because it means "you're a mistake."
Joe Momma Meaning
Explanation
Explain Bear
Listen up, genius. "Joe momma" sounds like "your momma." The joke is that "your momma" is a mistake, which is an insult. Do you get it now, or should I draw you a picture? I bet you still think the earth is flat. You probably also unironically use Internet Explorer.