Across the Irish countryside, peat bogs have long hidden ancient secrets beneath their cool, spongy surfaces. Among the more curious of these is bog butter—lumps of dairy fat, sometimes weighing over 40 kilograms, buried deep in turf and occasionally unearthed by modern turf cutters. But why would medieval (and even pre-medieval) Irish communities hide butter in a bog?
What Is Bog Butter?
Bog butter in wooden vessel. 15th -16th century. Found near Portadown, County Fermanagh, Ireland. In the Ulster Museum. Photo by Bazonka / Wikimedia Commons
Bog butter is precisely what the name suggests: butter—traditionally made from cow’s milk—deliberately buried in peat bogs. Over the centuries, the butter undergoes a transformation, developing a waxy texture and strong aroma due to the unique environmental conditions of the bog. The high acidity, low oxygen levels, and consistently cool temperatures combine to create a natural refrigeration system that preserves organic material remarkably well.
Some bog butter, however, is not butter at all. A study from the University of Bristol revealed that while many samples were dairy-based, others were made from animal fat—most likely tallow, which was commonly used for cooking, lighting, and even waterproofing.
Preservation and Protection
During the Iron Age and medieval periods, butter was far more than a common foodstuff. It was a precious commodity—used in cooking, as a cosmetic or salve, and even as a form of payment or tax. As such, preserving it was essential. In a time without refrigeration, burying it in a bog may have been a practical solution to extend its shelf life, particularly during warmer months.
According to Caroline Earwood in her 1997 paper “Bog Butter: A Two Thousand Year History,” many bog butter finds from the Iron Age to the medieval period were stored in containers made from wood, animal hide, or ceramic, often sealed with bark. These materials suggest intentional storage rather than accidental loss.
Burying butter may also have protected it from theft. Hidden in an anonymous bog, the butter was less likely to be discovered by raiders or passers-by than if it had been kept in a home or granary.
Other Theories: Offerings and Fermentation
Bog butter. 15th -16th century. Found near Enniskillen, County Fermanagh. In the Ulster Museum. Photo by Bazonka / Wikimedia Commons
Though preservation is the most widely accepted explanation, other interpretations exist. Some archaeologists and historians posit that bog butter could have had ritual or religious significance. The Irish, like many ancient cultures, may have offered food to spirits or deities as part of seasonal or funerary rites.
More intriguingly, some researchers suggest that bog burial may have been a form of food processing. Just as modern cheese or cured meat gains flavour through controlled ageing, butter buried in peat may have developed a distinct taste or texture appreciated at the time—though it is safe to say this would be an acquired taste by today’s standards.
Modern Discoveries
In recent decades, discoveries of bog butter have captured public interest. In County Meath, a 10-kilogram lump was uncovered by turf cutter Jack Conway. Other notable finds include a 35-kilogram barrel of bog butter in Kildare (dated to 3,000 years ago) and a staggering 45-kilogram chunk discovered in County Offaly in 2013—estimated to be over 5,000 years old.
Despite their age, many of these ancient specimens still retain a strong buttery smell. Savina Donohoe of the Cavan County Museum recalled handling one: “There was even a smell of butter in the room it was in.”
Though Irish celebrity chef Kevin Thornton once famously tasted bog butter, experts like Andy Halpin of the National Museum of Ireland advise against trying it. After all, even the most adventurous palate might baulk at a bite of Iron Age dairy.
Dr Lorris Chevalier, who has a Ph.D. in medieval literature, is a historical advisor for movies, including The Last Duel and Napoleon. Click here to view his website.
Top Image: Bog butter, made by Benjamin Reade and tasted by participants at the Oxford Symposium on Food and Cookery, 2012. Photo by Navaro / Wikimedia Commons
By Lorris Chevalier
Across the Irish countryside, peat bogs have long hidden ancient secrets beneath their cool, spongy surfaces. Among the more curious of these is bog butter—lumps of dairy fat, sometimes weighing over 40 kilograms, buried deep in turf and occasionally unearthed by modern turf cutters. But why would medieval (and even pre-medieval) Irish communities hide butter in a bog?
What Is Bog Butter?
Bog butter is precisely what the name suggests: butter—traditionally made from cow’s milk—deliberately buried in peat bogs. Over the centuries, the butter undergoes a transformation, developing a waxy texture and strong aroma due to the unique environmental conditions of the bog. The high acidity, low oxygen levels, and consistently cool temperatures combine to create a natural refrigeration system that preserves organic material remarkably well.
Some bog butter, however, is not butter at all. A study from the University of Bristol revealed that while many samples were dairy-based, others were made from animal fat—most likely tallow, which was commonly used for cooking, lighting, and even waterproofing.
Preservation and Protection
During the Iron Age and medieval periods, butter was far more than a common foodstuff. It was a precious commodity—used in cooking, as a cosmetic or salve, and even as a form of payment or tax. As such, preserving it was essential. In a time without refrigeration, burying it in a bog may have been a practical solution to extend its shelf life, particularly during warmer months.
According to Caroline Earwood in her 1997 paper “Bog Butter: A Two Thousand Year History,” many bog butter finds from the Iron Age to the medieval period were stored in containers made from wood, animal hide, or ceramic, often sealed with bark. These materials suggest intentional storage rather than accidental loss.
Burying butter may also have protected it from theft. Hidden in an anonymous bog, the butter was less likely to be discovered by raiders or passers-by than if it had been kept in a home or granary.
Other Theories: Offerings and Fermentation
Though preservation is the most widely accepted explanation, other interpretations exist. Some archaeologists and historians posit that bog butter could have had ritual or religious significance. The Irish, like many ancient cultures, may have offered food to spirits or deities as part of seasonal or funerary rites.
More intriguingly, some researchers suggest that bog burial may have been a form of food processing. Just as modern cheese or cured meat gains flavour through controlled ageing, butter buried in peat may have developed a distinct taste or texture appreciated at the time—though it is safe to say this would be an acquired taste by today’s standards.
Modern Discoveries
In recent decades, discoveries of bog butter have captured public interest. In County Meath, a 10-kilogram lump was uncovered by turf cutter Jack Conway. Other notable finds include a 35-kilogram barrel of bog butter in Kildare (dated to 3,000 years ago) and a staggering 45-kilogram chunk discovered in County Offaly in 2013—estimated to be over 5,000 years old.
Despite their age, many of these ancient specimens still retain a strong buttery smell. Savina Donohoe of the Cavan County Museum recalled handling one: “There was even a smell of butter in the room it was in.”
Though Irish celebrity chef Kevin Thornton once famously tasted bog butter, experts like Andy Halpin of the National Museum of Ireland advise against trying it. After all, even the most adventurous palate might baulk at a bite of Iron Age dairy.
Dr Lorris Chevalier, who has a Ph.D. in medieval literature, is a historical advisor for movies, including The Last Duel and Napoleon. Click here to view his website.
Click here to read more from Lorris Chevalier
Further Readings:
Caroline Earwood, “Bog Butter: A Two Thousand Year History,” The Journal of Irish Archaeology, Vol. 8 (1997), pp. 25–42.
Top Image: Bog butter, made by Benjamin Reade and tasted by participants at the Oxford Symposium on Food and Cookery, 2012. Photo by Navaro / Wikimedia Commons
Subscribe to Medievalverse
Related Posts