Nineteenth century songwriter, John Mason Neale wrote these lyrics based on the by then legendary English figure of King Wenceslas and put them to a 13th century tune, Tempus Adest Floridum, a Swedish song celebrating Spring:

Good King Wenceslas looked out on the Feast of Stephen,
When the snow lay round about, deep and crisp and even.
Brightly shone the moon that night, though the frost was cruel,
When a poor man came in sight, gathering winter fuel.

“Hither, page, and stand by me, if you know it, telling,
Yonder peasant, who is he? Where and what his dwelling?”
“Sire, he lives a good league hence, underneath the mountain,
Right against the forest fence, by Saint Agnes’ fountain.”

“Bring me food and bring me wine, bring me pine logs hither,
You and I will see him dine, when we bear them thither.”
Page and monarch, forth they went, forth they went together,
Through the cold wind’s wild lament and the bitter weather.

“Sire, the night is darker now, and the wind blows stronger,
Fails my heart, I know not how; I can go no longer.”
“Mark my footsteps, my good page, tread now in them boldly,
You shall find the winter’s rage freeze your blood less coldly.”

In his master’s steps he trod, where the snow lay dinted;
Heat was in the very sod which the saint had printed.
Therefore, Christian men, be sure, wealth or rank possessing,
You who now will bless the poor shall yourselves find blessing.

Here we find a brave, saintly and kindly King Wenceslas helping the poor and encouraging others to do the same. In Victorian England, a grim and impovrished landscape, however romanticized now, the song undoubtedly struck resonant chords. Child labor, squalid living conditions for most, and worse were 'normal' facts of daily living then.

Was Wenceslas real? Yes and no. He was actually a Duke before he was a King though. And he wasn't really very good. He wasn't good at all.

He was actually a 10th century Duke of Bohemia, Vaclav in his native tounge (Czech). Wenceslas was well known for his piety, if not his good deeds. His mother was appointed regent for him for a time when his father died. Wenceslas, then 13, was sent to live with his zealously religious grandmother. She encouraged him to take the throne from his mother by force and to then impose Christianity on the country.

So, an assasination plot (on his mother) was launched but de-bunked. Wenceslas' mother retalliated by ordering that his grandmother, (her mother-in-law, which tempers it a little), be executed. Wenceslas never forgave her for it an dwhen he became king, he banished her from Bohemia. He made building up the Church of Bohemia a personal mission and became famous for it.

He converted his subjects, however, by torturing and executing them. He ordered those who insisted on keeping their old religions hung or roasted alive in the marketplace. He formed alliances with Christian nations. The nobles were not pleased, particularly when he allied with Germany, long an enemy. Even his own brother joined in a plot against him. He invited Wenceslas to a religious feast on Sept. 20, 929 AD and murdered him. Wenceslas was on his way to mass at the time.

So, "Good King" Wenceslas was actually quite bad. And when he looked out on a feast, of Stephen or otherwise, he met his death, not a pauper. He was barely 20 years old at the time of his death, (a contrast to the Santa Claus type we've come to imagine when we hear the song) and had ruled in tyranny for only 5 years. In spite of his cruelty, and I suppose the explanation for his glorification lies here, he is the patron saint of Czechoslovakia. If that's a saint, I'd hate to see the sinners.