The wren's nest as said to be protected by lightning. Whoever tried to steal wren's eggs or baby wrens would find their house struck by lightning and their hands would shrivel up. Lightning was the weapon of the thunder bull-god Taranis, who often inhabited oak trees, and the wren was sacred to Taranis.
- Philip and Stephanie Carr-Gomm: The Druid Animal Oracle: Working with the Sacred Animals of the Druid Tradition

The oak is associated with long lifespan and wisdom. ... It is associated with male aspects of the sacrificial Mysteries. ... The Oak is the tree of Kingship, and was originally the soul-vessel of the sacrificial King. ... The oak is associated with lightning and the gods of lightning, such as Zeus or Jupiter, and the Celtic wheel and thunder god Taranis.
- R.J. Stewart, The Way of Merlin

Difficulty at the Beginning works supreme success,
Furthering through perseverance.
Nothing should be undertaken.
It furthers one to appoint helpers.
Clouds and thunder:
The image of Difficulty at the Beginning.
Thus the superior man
Brings order out of confusion.

'The wren, the wren the king of all birds
On St. Stephen's day he got caught in the furze.
Although he was little, the family was great.
Up with the kettle, down with the pan
Give us a penny to bury the wren.'

Stephen, whose name means "crown" was the first Christian martyr, stoned to death three years after the death of Christ. According to the church, the enemies of the church were furious at the success of his preaching. Catholic Online says, "They could not answer his wise argument, so they got men to lie about him, saying that he had spoken sinfully against God." He was accused of blasphemy and his defense, accusing the Sanhedrim of stubbornness and blindness toward the Holy Spirit, so enraged the council that they "rushed at him as one man, dragged him out of the city, and began to stone him." His story is related in Acts 7:58. His feast day was celebrated on December 26. This day is also known as the Boxing Day in reference to the annual distribution of cloth tools, shoes, spices, meat and cereals from the lord of the manor to his workers and the opening of alms boxes for the poor.

Did he doubt or did he try?
Answers aplenty in the bye and bye
Talk about your plenty, talk about your ills
One man gathers what another man spills
St. Stephen, words by Robert Hunter, music by Jerry Garcia

Sir Gawain and the Green Knight is an Arthurian tale written down in the fourteenth century. It tells a story hearkening back to the older celtic tale of Bricrui's Feast. At Yuletime, a knight all in green bursts into the feast hall offering the challenge of the Beheading Game. Only Gawain takes him up on it. After beheading the Green Knight, he must go to the Green Chapel a year hence and take the blow of the axe himself. When Gawain beheads the Green Knight, the Knight does not die, and Gawain goes through adventures in the process of fulfilling his end of the bargain.

The Green Knight is an instrument of the Goddess of Sovreignty. His story incorporates the ancient tradition of the Holly King, the King of Winter, the King of the Otherworld (Gwyn ap Nudd). He is the old year who cedes his place to the new year, in the person of Gawain, the Hawk of May, the King of Summer or Britain.

The beheading of the Green Knight expresses the same symbolic sacrifice of the old year to the new does the hunting of the wren.