Urban Legend: Boxing Day comes from the need to rid the house of empty boxes

False.
Few Americans have any inkling that there even is such a thing as Boxing Day, let alone what the reason might be for a holiday so named. However, before one concludes we’re about to rag on Americentric attitudes towards other cultures, we should quickly point out that even though Boxing Day is celebrated in Australia, Britain, New Zealand, and Canada, not all that many in those
countries have much of a notion as to why they get the 26th of December off. Boxing Day might well be a statutory holiday in some of those lands, but it’s not a well understood one.
Urban Legends Reference Pages: Holidays (Boxing Day)