Sancha as a "Devil" Mummer at the Fort Tryon Park Medieval Festival, Oct. 2005

There are two major branches to the tradition of the Mummers' Play (also known as mumming, and by various other regional names): firstly, the folk tradition of troupes of mummers performing theatre, sometimes in the street but more usually as house-to-house visits and in public houses; secondly, the more formal Christian Mystery plays.

No firm conclusions have been come to regarding the etymology of the word "mummer". It is usually believed to have originated from the Middle English word mum which means "silent" (suggesting that the plays were originally silent pantomimes), though some people have suggested a connection with mommo, the Greek word for "mask", or mumme, the Danish word for "mask". Other possible relationships exist with the words "murmur" and "mutter".

Mummers' and guisers' plays were formerly performed throughout most of Great Britain and Ireland, as well as in other English-speaking parts of the world including Newfoundland and Saint Kitts and Nevis. In England, there are a few surviving traditional teams, but there have been many revivals, often associated nowadays with Morris dance and Sword dance groups. Mummers and guisers can be traced back at least to the middle ages, though when the term "mummer" appears in ancient manuscripts it is rarely clear what sort of performance was involved. A key element was visiting people in disguise at Christmas. At one time, in the royal courts, special allegorical plays were written for the mummers each year - for instance at the court of Edward III, as shown in a 14th Century manuscript, now in the Bodleian Library, Oxford. However, apart from being in rhyme, these plays were nothing like the current traditional plays, whose documented history only goes back as far as the mid-18th century.

Although usually broadly comic performances, the plays seem to be based on underlying themes of duality and resurrection and generally involve a battle between two or more characters, perhaps representing good against evil. Usually they feature a doctor who has a magic potion which is able to resuscitate a slain character.

In mummers’ plays, the central incident is the killing and restoring to life of one of the characters. First, the characters are introduced in a series of short speeches in which each personage has his own introductory announcement; then comes the drama. The principal characters, presented in a wide variety of manner and style, are a Hero, his chief opponent and a quack Doctor; the defining feature of mumming plays is the Doctor, and the main purpose of the fight is to provide him with a patient to cure. The hero sometimes kills and sometimes is killed by his opponent; in either case, the doctor comes to restore the dead man to life.

The name of the hero is most commonly Saint George, King George, or Prince George. His principal opponents are the Turkish Knight (in southern England and Turkish Champion in Ireland), or a valiant soldier named Slasher (elsewhere). Other characters include: Old Father Christmas (who introduces some plays), Beelzebub, Little Devil Doubt (who demands money from the audience), Robin Hood (an alternative hero in the Cotswolds), Galoshin (a hero in Scotland), etc. Despite the frequent presence of Saint George, the Dragon rarely appears in these plays; the few instances can all be traced back to a Cornish script published by William Sandys in 1833.

Occasionally, the performers will wear face-obscuring hats or other kinds of headgear, which create the impression of being masked. More often, mummers' faces are blackened or painted red by way of disguise. Many mummers and guisers, however, have no facial disguise at all.

Local seasonal variants
Although the main season for mumming throughout Britain was around Christmas, some parts of England had plays performed around All Souls' Day (known as Souling or soul-caking) or Easter (Pace-egging). In north-eastern England the plays are traditionally associated with Sword dances or Rapper dances.

In some parts of Britai