The origin of the term chowder is obscure. One possible source is the French word chaudière, the type of cooking/heating stove on which the first chowders were probably cooked. (This, if true, would be similar to the origin of casserole, a generic name for a set of main courses originally prepared in a dish called a casserole.) Another possible (and maybe more probable) source could be the French dish called chaudrée (sometimes spelt chauderée) which is a sort of thick fish soup from the coastal regions of Charente-Maritime and Vendée.
The phonetic variant chowda, found in New England, is believed to have originated in Newfoundland in the days when Breton fisherman would throw portions of the day's catch into a large pot, along with other available foods.
Fish chowder, corn chowder, and clam chowder continue to enjoy popularity in New England and Atlantic Canada.