Okay a little back story Good King Wenceslas was published in 1853 by John Mason Neale the tune is a Finnish song “the time is near for flowering” which was published 300 years previous.
The song tells the tale of King Wenceslas who standing by his window on St. Stephen’s feast day (December 26) sees a peasant searching for firewood in the deep snow. He calls his page to him and inquires as to where the peasant lives. Finding that he lives “a good league hence” (roughly 3.4 miles) near Saint Agnes’ fountain in the woods. Taking provisions and firewood the King and page set out into the storm where the page begins to falter and tells the king that he can’t go on. The king tells the page to step where he steps and the cold will be abated the page does so and finds that where the saint has walked the ground is heated.
The real Wenceslas was a 10th century Duke (not a king) of Bohemia who was a Christian and spread the Christian faith through his country until he was murdered by his brother. Wenceslas is the patron saint of Czech Republic.