Maybe it was made by cleaver trolls. Like there were smarter giants in Narnia before the modern kind. Maybe the purse is like a parrot and learns to talk like creatures it is with. Another possibility is that is one of the magical toys the dwarves created.

Maybe the purse is like a parrot and learns to talk like creatures it is with. Another possibility is that is one of the magical toys the dwarves created.

I think the solution could be a combination of those two possibilities. The Dwarves are indeed said to have made many wonderful magical toys, that were sold at the market in Dale (before the arrival of the dragon), and they could have made such a one, which would pick up the language and the mannerisms of its owner(s).

It would indeed have been made by somebody more clever than these three ...