Throughout Great Britain, Canada, Australia, Commonwealth Countries where there is a large Christian population, Ireland (where it is known as St.Stephen's Day), South Africa (where is it known as the Day of Goodwill) 26 December (or the following Monday if it falls on a weekend) is known as Boxing Day. Elsewhere in Europe it is simply known as the 'second Christmas day'.
Most from these countries, if you ask them, will have no idea why it is called 'Boxing Day', though. It probably originated to assuage the consciences of the rich people in Britain whose employees were forced to work on 25 December catering to their festive needs. To compensate for their loss, they were given the following day off on which to visit their families. At the same time, they were given 'boxes' containing money, gifts and the food left-overs from their Christmas feasts to take home with them. In earlier Catholic England metal boxes were placed outside churches on St.Stephen's Day to collect special offerings for the saints...and so for the Church. By the 19th century in England a tradition arose by which the rich would give out 'Christmas boxes' on the day after Christmas to the tradesmen who served them in return for good service for the previous year. Employers caught on to this and gave their employees gifts and bonuses. I remember the tradition growing up in England when my mother would give money gifts to the milkman, rubbish collectors, and others and was regarded by the latter as one of the perks of the season.
In a nutshell, Boxing Day was originally the Poor Man's Christmas and a kind of alms-giving by the rich to the poor...in some cases arguably a form of token atonement for exploiting them for the rest of the year and a means to gain Stockholm Syndrome-like affection and loyalty in return.
Some who abandon Christmas but who want not to be seen to be antisocial are tempted to continue a kind of 'Boxing Day Tradition' by making collections for the poor. And whilst the poor should be assisted when our governments fail to do so using our compulsory taxation, it really ought to be done on a consistent basis throughout the year and not to gain social acceptance by observing a 'late Christmas' as Jews and Messianic Jews do in observing Hanukkah which was originally a late Sukkot before it was completely transformed into a pagan light festival like Christmas.
Retailers, of course, wishing to cash in on Christmas sales, not only eagerly promote Boxing Day but all the days between Christmas and New Year's Day to clear their unsold Christmas stocks. In Germany this is called zwischen den Jahren or 'the days between the years'. In other countries around the world this is therefore the period for large clearance sales. Like 'Black Friday', the day after American Thanksgiving, Boxing Day is a major business day. 26 December 2005 was the single largest economic transaction day in the history of Canadian commerce with individual stores able to gross over $1 million on a single Boxing Day. Indeed, there has been concern in the UK over the overpricing of goods scam at Christmas so that they can be 'reduced' for the Boxing Day 'sales'. It's also a big Sports Day in Canada (Ice Hockey), Northern Ireland (Premier league Football), England (Fox Hunting before it was banned, and now Football and Horse Racing) and South Africa (Test Match Cricket).
Some older pagan Boxing Day traditions survived in Wales as late as the 19th century that included the bleeding of livestock, and the beating of late risers and female servants with holly branches that drew blood (hence it was also known as 'slashing').
Whatever Boxing Day may have been or is, it has absolutely nothing to do with the Gospel of Yah'shua the Messiah (Jesus Christ). It belongs wholly to the world system - it's basically just another extravagent Christmas-like shopping day - and should play no part whatsoever in the lives of Bible-believing Christians and Messianics. It's just another working day (unless it falls on a Sabbath) and should be treated as such...with one exception: it happens to be the birthday of one of my sons so we celebrate Yahweh bringing him into the world on that day!