Yule log

The Yule log, Yule clog, or Christmas block is a specially selected log burnt on a hearth as a Christmas tradition in a number of countries in Europe. The origin of the folk custom is unclear. Numerous scholars have observed that, like other traditions associated with Yule (such as the Yule boar), the custom may ultimately derive from Germanic paganism.

In Santa Claus, A Biography, historian Gerry Bowler notes that the yule log was one of the most widespread Christmas traditions in early modern Europe, with the first recording of its appearance dating to 1184. Bowler notes that the tradition's roots are debated -- some saying it is an "enfeebled version of the ancient Celtic human sacrifices" and others saying it's simply related to a feudal obligation of acquiring firewood. Nevertheless, the log was a huge block, lasting for the Twelve Days of Christmas, and it was not burned completely its first year: part of it was saved to light the following year's yule log. While the mostly burned wood waited for its duty to light a new yule log, it was kept around the house to ward off a range of misfortunes, including toothaches, mildew, lightning, housefires, hail and chilblains (an inflammation of small blood vessels brought on from exposure to cold). The log had other magical properties, particularly in parts of Northern Spain and Southern France. There, Bowler notes, "a remarkable feature of the log's powers is its ability to defecate gifts."

According to the Encyclopedia of English Folklore, the first "clear" references to the tradition appear in the 17th century, and thus it is unclear where or when the custom extends.

However, it has long been observed that the custom may have much earlier origins, possibly extending from or echoing customs observed in Germanic paganism. As early as 1725, Henry Bourne sought an origin for the Yule log in Anglo-Saxon paganism:

...
Wikipedia