It also seems to me that expressions drift away faster than other aspects of the language. Perhaps due to their casual nature, or due to context. And they’re often extremely local, too - for example, I’ve heard nordestinos using “sacrifício de mundo” (lit. world sacrifice) to refer to difficult things, while folks here in Paraná practically never do it. While saying that something is “uma vaca no milharal” (a cow in the corn farm - wrecking everything with no regards or reason) usually outs the person as from a rural background.

For speakers from Portugal there’s an additional weird expression: pila is used here in Paraná as a completely innocent word for money, e.g. “dois pila” two bucks. (In PT I believe that it’s used as a slang for dick.)