Brewer's: Yule Log
A great log of wood laid in ancient times across the hearth-fire on Christmas Eve. This was done with certain ceremonies and much merry-making. (Norwegian, juul, Christmas.)
Ever at Yuletide, when the great log flamed In chimney corner, laugh and jest went round.
Aldrich Wyndham Towers, stanza 5
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894