boxing day · noun1
From Boxing Day.
Boxing Day · noun2
Perhaps because of boxes that were placed outside churches to collect special offerings tied to St. Stephen's Day; or because of the old British custom of tradesmen collecting “Christmas boxes” of money or presents on the first weekday after Christmas as thanks for good service, mentioned by the English diarist Samuel Pepys (1633–1703).
Etymology from Wiktionary, CC BY-SA 4.0.