I don't recognise it from a carol, but it could be from the apocryphal verse of Good King Wenceslas:

Page & Monarch off they went, for peasant hunting thrill.
"That seems a good place to try, look, up yonder hill"
Up they went through drifts of snow. A struggle? Yes, and how.
At the top they found the serf, the wanker sto-ood on the brow!