What does it mean for a boy to name himself an old sow?

Is a humorous, teasing or playful way, used for well-meaning jokes or jokes.

This naming method is not to belittle yourself literally, but to express a certain trait, character or behavior in an exaggerated and humorous way. In intimate relationships and friendly environments, people will use such nicknames to increase their interest in interaction and show their relaxed and happy communication. It doesn't mean that boys are actually compared to sows, but it embodies a playful and humorous style.