E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
The great feast of Saturn was held in December, when the people decorated the temples with such green things as they could find. The Christian custom is the same transferred to Him who was born in Bethlehem on Christmas Day. The holly or holy-tree is called Christsthorn in Germany and Scandinavia, from its use in church decorations and its putting forth its berries about Christmas time. The early Christians gave an emblematic turn to the custom, referring to the righteous branch, and justifying the custom from Isaiah lx. 13The glory of Lebanon shall come unto thee; the fir-tree, the pine-tree, and the box together, to beautify the place of my sanctuary.