Okay, here's one that I suspect only the Christmas Music Guru can answer:

According to Wikipedia  "Sheep May Safely Graze" was "originally written for a birthday celebration, that of "Christian, Duke of Saxe-Weissenfels."  Tthe image of the shepherd was to represent the Duke and the sheep to represent his subjects whom he protected.

So, when did it become associated with Christmas, and when was it first recorded on an album of Christmas music?