1) A small cask used to store or transport a variety of provisions.
1483 3 ferthkynnes sturgeon, Hull
1527 Item half a Barell of Butter & a firkin, Whitby
1554 The brewehowse ... x ferkyns a berestande, Brantingham
1669 2 firkins of butter, Elmswell. It was originally equivalent to a quarter of a barrel and half a kilderkin.