Of course, the Brotli default (built-in) dictionary is infamous for containing such strings like "Holy Roman Emperor", "Confederate States", "Dominican Republic", etc., due to the way it was created. One can see the whole dictionary in https://gist.github.com/duskwuff/8a75e1b5e5a06d768336c8c7c37....

Having a dictionary created by actual content to be compressed will end up with a very different dictionary.