From Wikipedia:
"Good King Wenceslas" is a popular Christmas carol about a king who goes out to give alms to a poor peasant on the Feast of Stephen (the second day of Christmas, December 26). During the journey, his page is about to give up the struggle against the cold weather, but is enabled to continue by the heat miraculously emanating from the king's footprints in the snow. The legend is based on the life of the historical Saint Wenceslaus I, Duke of Bohemia (907-935), known in the Czech language as Svatý Václav.
The legend is an old one, but its power is such that it has persisted for more than a millennium. Considered a martyr and a saint immediately after his death, a cult of Václav grew up in Bohemia, and also in England. Within a few decades of Václav's death four biographies of him were in circulation. These hagiographies had a powerful influence on the High Middle Ages conceptualization of the ‘’rex justus’’, or “righteous king”—that is, a monarch whose power originates not merely from the unconditioned Divine Right of Kings, but which stems mainly from his great piety, as well as from his princely vigor."
