chowderhead

The chowder in chowderhead is neither New England nor Manhattan (though one could speculate that a chowderhead has either type of clam chowder for brains). Chowderhead is a mispronunciation of jolterhead, a derivative of the 16th-century insult jolt head. Before being extended to a thickheaded person (i.e., a blockhead), the term jolt head was used literally for a large, heavy head. The etymology of jolt head is obscure; the term is likely connected somehow to the jolt that means "an abrupt jerky blow or movement," but the exact nature of the connection is not known.