Folk linguistics

Folk linguistics is when people who aren't experts in language study the way people speak and use words. It's like people playing armchair experts and thinking about how people talk. For example, one person might say something like "it sounds like this is an old-fashioned way of speaking" or "that's an expression people don't use anymore". People can even make up their own words and catchphrases which can become popular if a lot of people use them.