Definition of "stockfish"

So the Prior of Saint Botolph’s hobbled back again into the refectory, to preside over the stockfish and ale, which was just serving out for the friars’ breakfast.

1819, Walter Scott, Ivanhoe

We saw the codfish here in all the stages of preparation for the table and the market; the stockfish, dried in the open air, without salt; crapefish, salted and pressed

1856, Elisha Kent Kane, Arctic Explorations