Boxing Day (n.)youdaoicibaDictYouDict[Boxing Day 词源字典]
1809, "first weekday after Christmas," on which postmen and others expect to receive a Christmas present, originally in reference to the custom of distributing the contents of the Christmas box, which was placed in the church for charity collections. See box (n.1). The custom is older than the phrase.[Boxing Day etymology, Boxing Day origin, 英语词源]