"Cod pieces" are items of clothing worn by men in the past, especially during the Renaissance period. They are pouches or coverings worn over the groin area. Full definition
In a large bowl, cover the cod pieces with 2 inches of cold water and soak, chilled, at least 24 hours and up to 36 hours, changing the water 2 to 3 times per day and tasting the cod to test for saltiness after the first 24 hours. (epicurious.com)