Question: WHY is the 26th called 'Boxing Day'??
I have read various reasons. The most widely accepted - I believe - is that people from the "Lower Classes" would be given gifts from their employers - in small boxes - which they would open the day after Christmas. And workers in shops would open the collection box - left out for "tips" on the 26th.
As a child in England I recall that adults would still talk about the "Christmas Box." A small monetary gift for the Paper Boy, or "Bin Men."
It is an English/British thing. Spread to various English-speaking countries but not USA.