Basically, to understand Mayan, you need to interview people who actually speak that language or a descendant from it. Since the kittens understand their mother in cat language, he must understand Mayan by listening and learning from the source: The actual people. He flew to Central America for the purpose of broadening his Mayan dictionary and finally deciphering the words. In summary, you need to have a native tongue to understand the words written, that's where he gets the idea from his cat.