This slang term comes from the Chow Chow breed of dog, known for its distinctive blue-black tongue and fluffy coat. While the term itself isn't widely used, it's a playful reference to the breed's association with food, particularly in Chinese cuisine.
However, it's important to remember that using any animal breed as slang for food can be considered disrespectful and insensitive. It's best to use appropriate and respectful language when talking about both dogs and food.