There are several theories about this, but they all have to do with the idea of giving - basically, a box of gifts, usually money. Boxing Day, 26 December, is also St Stephen's Day, and this day had a long tradition of giving charity to the poor.

The Boxing Day name seems to be of British origin, though some other countries have similar festivals. As early as the 17th century it was common for employers to give their servants a box of money or presents, on Christmas Day or the day after; the tradition of giving something on the next day may have started because servants would have to work on Christmas Day but might be given the 26th December off to visit their families.

Another reason for the name is the custom of opening the collection boxes that were kept in the churches, and handing out the money to the poor on this day. The day continues to be a public holiday in the UK and several other countries.