Private language argument

The Private Language Argument is an argument that says only you can understand words that you make up. For example, if you created a word like “floozle” and only you knew what it meant, other people wouldn't understand it because it doesn't have a real meaning - it's just made up. The argument also says that all language is like this - words only have meaning because other people understand them, not because we make them up ourselves. So, if nobody else can understand our language it is impossible for us to truly understand it either.