‘Mouth Breather’
Like yeah I don’t get this one. We all breathe through our mouths (and noses), because we have to. Yet I read this sometimes as it is used like an insult. So what are you saying? You’re insulting someone for doing what billions of other human beings have to do naturally?
Because humans are awful, mouth breather probably comes from Down syndrome and the associated physical traits of a proportionally large tongue and narrow mouth.