On Christmas days, 25th December, Christians usually visit Church and leave money and gifts for the less wealthy people and social inferiors in small boxes known as Christmas Box.
In olden days, the poor servants used to work in their master's place on the Christmas day. Thus, they will enjoy a holiday on the following day, 26th December. Servants would bring small boxes in which their masters kept coins and food.. as bonus!
Even today, Christmas bonus hasn't changed, neither has the public holiday the next day of Christmas. Employees might not bring those Boxes to their employers anymore but to mark the days gone by, since 1980, Cricket Australia hosts a cricket test match at Melbourne cricket ground, starting 26th December every year, between Australia and a touring team.
Thus the name derived-Boxing day test.
The Boxing day test was first played in 1950 in Melbourne. From 1953 to 1967, no such test were played. But the tradition was started again with tests being played on this day either in Australia or other country. However from 1980, the Melbourne Cricket Club and the Australian cricket team secured the rights to play the match annually and has been going on since then except in 1989 where a boxing day ODI was played
In 2009, Pakistan and Australia will be playing the Boxing day test match. It will be the first test of the 3-match series.
Pakistan had already played a boxing day test match in 2004 where it lost by 9 wickets and in 1983 where it was a draw. Australia has won 9 out of last 10 boxing day test matches, the loss being in 2008.