In England, the day after Christmas is called Boxing Day, which I used to think had something to do with pugilism. Then I thought it was the day that people boxed up their Christmas gifts. But a friend of mine from the UK (who used to hold a Boxing Day party every year) gave me a different explanation. England, Australia, and Canada all celebrate Boxing Day; originally, December 26 was the day that service workers received a "Christmas Box" from employers.
Here in the states, we tend to tip our doormen, garbage collectors, postal carriers, and anyone else who serves us during the year before the holiday, not after. So if you've forgotten your reliable dog walker or loyal babysitter this year, there is still time--take a page from the Brits, and hand them a "box" of holiday cheer!