A sheela-na-gig is an ancient stone carving of a naked woman displaying prominent, often grossly enlarged genitalia. The term "sheela-na-gig" comes from the Irish language, and is usually interpreted as a variation of Sighle na gCíoch (meaning "the old hag of the breasts") or Síle-ina-Giob ("old woman on her hunkers"). Sheela-na-gigs are quite prevalent in Ireland, usually carved into the stone archways or walls of old churches and castles. They can also be found throughout Scotland, England, Wales, and on the European continent in France and Spain. The original function of sheela-na-gigs is lost to history.

Sheela-na-gigs generally portray a woman squatting or in a seated position (although some seem to depict women who are standing). The woman's legs are invariably splayed wide open, the better to display her genitals, which can be as rudimentary as a simple slit, or may include crudely carved labia, vulva, and sometimes the clitoris. Her hands may be crossed over her abdomen or gesturing to her pudenda, but are often carved as directly gripping the labia to expose the vulva. Sheela-na-gigs usually have oversized genitals and heads, with smallish or absent breasts. Many are portrayed as emaciated or deliberately grotesque, with visibly exposed ribs and exaggerated facial features, including bulging eyes, a protruding tongue, and striations on the cheeks and forehead that may indicate wrinkles or tattoos. They vary between 10 cm to 60 cm (approximately 4 inches to 24 inches) in height. The method of carving also varies, from simple lines etched into the stone, to low or high relief.

There are many theories regarding the origin and function of sheela-na-gigs, which can be classified into two schools of thought. One theory is that the sheela-na-gigs are indicative of goddess worship and were perhaps used in fertility rites or as symbols of protection. This is a rather unlikely explanation due to the age and location of the vast majority of sheela-na-gigs: most are carved into the stones of Christian churches erected between the 13th and 17th centuries (although some are located on secular buildings that were erected during the same time period). The sheela-na-gigs are also missing some of the primary characteristics of goddess and fertility figures found in other parts of the world, such as enlarged breasts and hips, and other symbols of motherhood. Supporters of this theory (mostly Celtic wiccans and Irish feminists) argue that the sheela-na-gig's haglike appearance represents a goddess in her crone stage.

A second explanation is that the sheela-na-gigs were meant to serve as warnings against the sins of lust and promiscuity. The timing of the appearance of the sheela-na-gigs roughly coincides with the Norman invasion of England and Ireland, as well as the Roman Catholic Church's attempts to standardize the practice of Christianity throughout Western Europe. Until this time period, Irish Christianity had comfortably assimilated many traditions that were considered sinfully pagan by the Church, and the sheela-na-gigs may have been a medieval attempt to discourage "pagan" practices like marriage within the clergy. The fact that the sheela-na-gigs appear largely on Norman-style churches and are vaguely reminiscient of Romanesque figures supports this theory that they were imported from the continent by the Normans. It also explains why there is nothing in Irish lore or tradition regarding the origin or function of the sheela-na-gigs.

Sheela-na-gigs first came to the attention of the scientific community in 1840, when the Royal Irish Academy studied several such exhibitionist figures located on churches in Tipperary County, particularly one on an outside wall of Kiltinane church (unfortunately, this mother of all sheela-na-gigs was stolen by an enterprising thief in 1990 and has never been recovered). However, the term "sheela-na-gig" has been in use since at least the early 17th century. The explicit, almost aggressive sexuality of the carvings has caused much controversy, and sheela-na-gigs have had many (often derogatory) names throughout the ages, including the Devil Stone, Evil Eye Stone, Hag of the Castle, Whore, Julia the Giddy, and Sheila O'Dwyer.

Some pictures of sheela-na-gigs:
http://www.members.tripod.com/~taramc/photos.html

Sources:
Kelly, Eamonn. Sheela-na-Gigs: Origins and Functions. Dublin: Country House. 1996.