Why is he called Huckleberry Finn?

Excuse me, but I couldn't help but notice the title 'Huckleberry Finn.' It's quite a unique name, and I'm curious to know the origin behind it. Is there a specific reason why the protagonist of this story is called Huckleberry Finn? Is it a nickname that he acquired, or does it have deeper significance to the plot or character development? I'd be grateful if you could shed some light on this intriguing detail.