Lots of kids make a common, but very logical, language mistake. If they don't do something 'on purpose,' then it must have been done 'on accident.' It is not correct, but it makes sense. It reminds me of a quote I used to have on a chart: If English were sensible, lackadaisical would have something to do with a shortage of flowers.
Language does adjust and change as people use it. Nauseous is officially defined as "offensive to the taste or smell, disgusting, repellent." Yet I hear people all the time using it to describe themselves, "I was nauseous all day," or "the whatever made me nauseous." I'm certain they weren't saying that they were disgusting and offensive, causing others to be affected with nausea.
The adjective they should have used is nauseated, but that is an extra couple of syllables, or it sounds less cool--I don't know.
However, if enough people used a word incorrectly, it becomes okay. My dictionary says, "Today, however, the use of nauseous to mean 'affected with nausea' is so common that it is generally considered to be standard." I'm probably going to be out of step for a while longer.
One last thing I've noticed is some people have an itch and itch it. When I have an itch, I scratch it. Has anyone else heard someone say they are itching a bug bite? Is it a local thing? My hubby claims not to have heard it used that way, but he's not the world's best listener.