In Britain, Christmas Box was used to describe a Christmas present. Though the tradition of charity goes back to the Catholic Middle Ages (see the legendary history of St. Wenceslaus), in Victorian times, Boxing Day became an official holiday, a servants' day off, and they were given a Christmas Box from their employers, which they would take-home to share with their families. The custom spread throughout the British Empire.
Though still connected to fox hunts and football, like so many holidays, Boxing Day has largely fallen victim to the cultural meta-narrative of commodification, a day for sales and bargains, and frenzied competition between sellers and tussles between buyers. Have a look at this report from Australia. EU visitors and wealthy tourists from China and the Middle East could join the locals and spend as high as £4 billion on 26th of December alone.
US Americans, already exhausted by the Black Friday, the day after Thanksgiving sales, and Cyber Monday the following week, as well as by the Christmas holidays are more likely to stay home and perhaps not even shed their pajamas on the 26th if they have the day off, perhaps surprising to Commonwealth visitors. Yes, there will be post-Christmas sales, but the day after Christmas in the USA is largely one of recuperation, though many have to return to work.
For those who wish to continue the tradition of charity can use the 26th, also known as St. Stephen’s Day in other places, as a time for contributions to charities, given that we are surrounded by seemingly endless humanitarian crises. I hope you will join me in doing so. In some places, there is also a tradition of jumping into the icy sea for a Boxing Day dip or swim while contributing to a local charity. I think I'll pass on that.