The high acid content of the soil gives bogs great preservative qualities. It turns out that between the 6th and 19th centuries A.D., people in Ireland and Scotland buried their butter in bogs, making butter one of the most widespread archaeological items found in bogs.
Why? Since refrigerators did not exist in those days people had to rely on the peat to protect the butter from daytime heat stop it from growing mould. To help preserve the butter in earlier times, 5% or more salt was added to it. Then, before the butter could be eaten, slices of it were first soaked in water to reduce the salt content. If salt was scarce or unaffordable, the cold, anaerobic, antiseptic peat offered an alternative way to preserve butter through the autumn and winter. It also provided a way to preserve garlic butter, a special kind of butter made especially for use during Lent. Salt could not be used to preserve garlic butter because soaking in water before use would remove the garlic as well as the salt. Unfortunately, there are very few accounts of “bog buttering”, which might give an accurate picture of how it was actually buried in a way that would ensure preservation.
This suggests one of the primary reasons for burying butter, was a to preserve special types of butter made for certain, most likely festive seasons. Storage over a period was necessary to allow the added flavouring to penetrate the fat and season the butter evenly. Burial in a bog would ensure protection from daytime heat and keep the butter as cool as possible, while the exclusion of air, and the antiseptic qualities of the turf would prevent mould growth.
The containers in which the butter was buried give clues on the date of the “burial”. These containers were made from a variety of materials, including wood, bark, cloth, wickerwork and animal skins. The wooden vessels are sometimes carved out of a solid piece of wood, with a detachable lid or handle. Sometimes the base is a separate piece, cleverly inserted. Some vessels are made of stays. Carefully decorated wooden containers have been found, indicating how highly prized they were.
An account on Irish food written by Dinely in 1681 contains the following description: “Butter, layed up in wicker baskets, mixed with a sort of garlic and buried for some time in a bog to make a provision of an high taste for Lent”.
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