The Cajun and Creole cooking term for an onion, celery, and bell-pepper flavor base is the holy trinity.
The holy trinity is a foundational mixture used in Louisiana cooking, particularly in gumbos, jambalayas, étouffées, sauces, and many rice dishes. The vegetables are commonly chopped and softened in oil or butter before other ingredients are added.
It is related to the French mirepoix, which traditionally uses onion, carrot, and celery. Louisiana cooks replaced the carrot with green bell pepper, reflecting local ingredients and the development of regional Creole and Cajun foodways.
The proportions are not fixed, and some recipes add garlic, green onions, or parsley. The phrase describes the core three vegetables, not a spice blend and not a finished sauce. It is therefore different from roux, which is flour cooked with fat and used for thickening and flavor.