Take a wild guess at what that means. Yup, if you guessed something to do with a red-nosed reindeer, you get a prize.
It's quite amusing that someone decided to translate "Rudolph, the Red-Nosed Reindeer" into Latin and then set the text to a Gregorian chant melody, one that if a Youtube commenter is correct, is mostly an actual melody. There are two places in the song where it doesn't seem to match. The one I'm quite fond of is at "O Rudolphe..." because, let's face it, that's the most fun part of the song! It's also quite clever that "Sanctus Nicholas..." still resembles the original melody we all know while still sounding like chant. Job well done. Truly, it's marvelous.