One interesting bit of language evolution that seems to have run its course over the last twenty years is the loss of the distinction between "nauseous" and "nauseated". Historically, "nauseated" has mean that you were sick, and "nauseous" meant that you were making others sick.
In 2009, everyone I know describes their stomach troubles with "I'm nauseous." This is a usage that used to make my father, the general surgeon, react every time. But now when I laughingly agree that "yes, you are a bit nauseous" everyone just looks at me funny.
Language. Go figure. (B)