Recently, Jack Conway was “cutting turf," the term for digging up blocks of moss in Emlagh peat bog in County Meath, Ireland, when he discovered a 22-pound lump of butter. The find, believed to be 2,000 years old, according to the Irish Times, isn't an unusual occurrence in Ireland, where every year, people digging up peat moss to heat their homes encounter chunks of the dairy.

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The discoveries, which are called Bog Butter, can be thousands of years old. In 2009, a 77-pound, 3,000-year-old oak barrel of the stuff was found in County Kildare. In 2013, a turf cutter in County Offaly found a 100-pound, 5,000-year-old chunk. Many examples of the butter are found in Irish museums, including the place dedicated to the golden spread, Cork’s Butter Museum.

So what is Bog Butter? It's exactly what it sounds like—butter made from cow's milk, buried in a bog. What makes it special is its age. After spending so much time in the cool, damp peat, it starts to take on the appearance and consistency of paraffin wax. According to a study on bog butter by researchers from the University of Bristol, some of the chunks are non-dairy. When analyzing carbon isotopes in nine samples of the butter, they found that six of them were indeed dairy products, while the other three were from animals, perhaps tallow (rendered fat) stored for later use.

In a paper published in the Journal of Irish Archaeology, Caroline Earwood explains that bog butter is usually found in earthenware pots, wooden containers, animal skins, or wrapped in bark and takes on a pungent, cheesy odor. Looking at over 274 instances of bog butter from the Iron Age to medieval times, Earwood concluded that early Celtic people probably sunk the butter in the bog simply to preserve it or protect from thieves. The cool, low-oxygen, high acid environment of the bog made a perfect natural refrigerator. Seeing as butter was a valuable commodity and was used to pay taxes, saving it for times of drought, famine, or war would have been a good idea.

There are other theories about the butter as well. It could also have been buried in the bog as an offering to the gods or spirits, the Irish Times notes. The Bristol researchers wonder whether burying the butter in the peat was a type of food processing that changed the chemical composition of the butter to make it tastier.

Savina Donohoe, Curator of Cavan County Museum, which accepted Conway’s butter lump before sending it to the National Museum of Ireland for analysis, tells UTV Ireland the Conway’s big pat is thought to be thousands of years old, but that won’t be confirmed until researchers test the twigs and bark stuck to the butterball. Donohoe, who handled the stuff, said it smelled familiar.

“It did smell like butter, after I had held it in my hands, my hands really did smell of butter. There was even a smell of butter in the room it was in,” Donohoe says.

Though Irish celebrity chef Kevin Thornton took a bite of bog butter in 2014, Andy Halpin, assistant keeper at the National Museum’s Irish Antiquities Division, advises the Irish Times that it’s probably not wise to sample the Iron Age delicacy.

For those curious, Ben Reade, head of Culinary Research and Development at Nordic Food Lab created his own ancient butter recipe back in 2012. Reade's guinea pigs had mixed things to say about the taste. “The organoleptic [sensory] qualities of this product were to many surprising, causing disgust in some and enjoyment in others,” he writes. “The fat absorbs a considerable amount of flavor from its surroundings, gaining flavor notes which were described primarily as ‘animal’ or ‘gamey’, ‘moss’, ‘funky’, ‘pungent’, and ‘salami’.”