"After(s)" sometimes people say it instead of dessert, or one of my pet peeves-"pudding". I was confused about the double meaning of "pudding" for about a month, month and a half before I mentioned it to DH. Sometimes DH says "afters".
The 'after' I was meaning is the vague sort of one, because I hear it used all sorts of ways, including 'I'll be over after.' Again, after what?
Afters instead of dessert threw me at first, but I much prefer it to 'pudding', because I agree, pudding should be smooth, creamy and made from a Jello pudding mix and milk.

While instead of until threw me for a long time, and I still have to think about it for a bit from time to time.
Another one that always confuses me is 'stop' instead of 'stay'. It does make sense if you think about it, but it still confuses me. The first time I heard 'Are you going to stop in tonight?' I took it to mean the person asking if we were going to stop by their place, but she was asking if we were going to stay in.