Stir-up Sunday is an informal term in Anglican churches for the last Sunday before the season of Advent. The Christmas pudding is one of the essential British Christmas traditions and is said to have been introduced to the Victorians by Prince Albert, husband of Queen Victoria. The reality is that the meat-less version was introduced from Germany by George I in 1714. 
Traditionally, families gather together in the kitchen of their homes to mix and steam Christmas pudding on a Stir up Sunday. Parents teach their children how to mix ingredients for the pudding. Everyone takes a turn to stir the pudding mix for each person involved is able to make a special wish for the year ahead. (In reality, stirring the mixture is hard work, therefore as many as possible are involved.)
In some households, silver coins are added to the pudding mix.  It is believed that finding a coin brings good luck. Nowadays, sterilised (i.e. boiled) silver coins are placed under each serving on Christmas Day to avoid emergency visits to the dentist - and intra-family arguments!
In recent times, two-thirds of British children surveyed, revealed that they had never experienced stirring Christmas pudding mix. It comes with their parents' preference for ready made-mix of puddings available in grocery stores.
History and Etymology
The term comes from the opening words of the collect for the day in the Book of Common Prayer of 1549 and later (a translation of the Roman Missal's collect "Excita, quæsumus" used on the last Sunday before Advent):
- Stir up, we beseech thee, O Lord, the wills of thy faithful people; that they, plenteously bringing forth the fruit of good works, may of thee be plenteously rewarded; through Jesus Christ our Lord. Amen.
- Excita, quaesumus, Domine, tuorum fidelium voluntates: ut divini operis fructum propensius exsequentes, pietatis tuae remedia maiora percipiant: Per Christum Dominum nostrum. Amen.
In the Book of Common Prayer of 1662 and later, this collect is listed for "The Twenty-Fifth Sunday After Trinity", with a rubric specifying that this collect "shall always be used upon the Sunday next before Advent". This reinforced the significance of this day as forming part of the preparation for the season of Advent. The rubric is necessary because the last Sunday before Advent does not always fall on the twenty-fifth Sunday after Trinity: Trinity Sunday is a moveable feast and the Advent season is fixed, so the number of weeks in between varies from year to year.
Thus, this collect always was read just before Advent. Since most recipes for Christmas pudding call for the pudding to be kept for several weeks to mature, the day subsequently became connected, in countries which used the Book of Common Prayer, with the preparation of Christmas puddings in readiness for Christmas. Supposedly, cooks, wives and their servants would go to church, hear the words 'Stir up, we beseech thee, O Lord...', and be reminded, by association of ideas, that it was about time to start stirring up the puddings for Christmas.
In recent years most provinces of the Anglican Communion have adopted the practice of the Roman Catholic Church in observing this Sunday as Christ the King (sometimes under the name The Reign of Christ). Popular attachment to the Stir up collect has, however, caused it to be retained (in contemporary language) in the liturgies of several provinces. The Church of England's Common Worship uses it as the Post-Communion prayer, with a rubric stating that it "may be used as the Collect at Morning and Evening Prayer during this week".
In the Episcopal Church, USA, the collect appointed for the Third Sunday of Advent in the Book of Common Prayer (1979) begins with the phrase "stir up your power O Lord." Thus, in many Episcopal Churches, the Third Sunday of Advent, also known as Gaudete (rejoice) Sunday, is referred to as "stir-up Sunday." Marion J. Hatchett in his definitive work Commentary on the American Prayer Book, notes that in the Pre-Reformation English Sarum Rite, collects for four of the last five Sundays before Christmas began with the word excita or "stir up." A similar collect to the one appointed in the BCP 1979 appears in the recent book authorized for use in the Church of England, Common Worship, appointed for the Second Sunday of Advent, but the phrase "raise up" is used instead.
- Oxford English Dictionary. Second edition, 1989 (first published in New English Dictionary, 1917). "Stir-up Sunday (colloq.): the Sunday next before Advent: so called from the opening words of the Collect for the day. The name is jocularly associated with the stirring of the Christmas mincemeat, which it was customary to begin making in that week."
- Who needs Nigella? Stir-up Sunday: the idiot’s guide to home-made Christmas pudding Retrieved 24 July 2013
- This weekend is Stir Up Sunday – traditionally the time to make your Christmas pudding Retrieved 24 July 2013
- Christmas Pudding "Stir Up Sunday" Retrieved 24 July 2013
- Stir-Up Sunday – Time to make a start on Christmas Pud! Retrieved 24 July 2013
- Gary Cleland (24 November 2007). "Home-made Christmas puddings die out". The Telegraph. Retrieved 30 December 2010.