Where did the word Jul come from?
The word Jul is mentioned the first time in Haraldskvadet from about 870, where Thorbjørn Hornklofi sings about Harald Hårfager:
Ude på havet vil han drikke jul
den højtstræbende konge
om han skal kunne herske
Upon the sea he shall drink jul
the ambitious king
if he shall be able to rule.
This source and other later sources show that jul in the ancient period and in the Middle Ages was a solstice feast, where people celebrated the returning of the light with drinking bouts. The vikings had their "juleblot" where they sacrificed to their pagan gods, drinking to their honour - partly thanking and partly securing a good growth and a good profit on their raids in the year to come.
As early as year 400 the Church Father Johannes Chrysostomos mentions the Christian Jul as "the mother of all feasts." Although it was celebrated as the birth of Christ he was hardly born in December - but the early leaders of the church knew that it was easier to spread Christianity if they showed some tolerance to the customs and traditions which pagan people had worshipped for generations. Therefore the Roman Saturnalia-feast in December was in year 354 linked to the birth of Christ and thereby turned into a Christian celebration.
source: Ruth Gunnarsen: Familiens højtider i gamle dage.
photo 2004: grethe bachmann, Mindeparken , Århus