Dr J R Stockton wrote on 28 dec 2011 in comp.lang.javascript:
It appears that the Dutch celebrate Christmas (and Easter Sunday and
Pentecost) so inefficiently, or so comprehensively, that they have each
for two days each year.
Celebremus diem festem, sodales!
Most Dutch don't celebrate it, we just have both days off.
Possibly the second day originally was to recuperate from the religiously
strenuous and/or food-wize copious first day?
However we don't like to go boxing that second day,
like efficient or comprehensive Britons do.
[Today, Boxing Day is better known as a bank or public holiday that occurs
on December 26, or the first or second weekday after Christmas Day,
depending on national or regional laws. It is observed in the United
Kingdom, Australia, Canada, New Zealand, and some other Commonwealth
nations.
....
The exact etymology of the term "boxing" is unclear, and there are several
competing theories, none of which is definitive.
....
In the UK, it was a custom for tradesmen to collect "Christmas boxes" of
money or presents on the first weekday after Christmas as thanks for good
service throughout the year.
Wikipedia]