The “Trinity” means different things to different people. It means one thing to a pastor, another to a cook.
The chopped vegetable base is found in recipes from around the world.
A mirepoix (/mɪərˈpwɑː/ meer-PWAH; French pronunciation: [miʁˈpwa]) is a mixture of chopped onions, carrots, and celery (either common pascal celery or celeriac). (Traditionally: 2 parts onions, 1 part carrots & 1 part celery.) Mirepoix, raw, roasted or sautéed with butter or olive oil, is the flavor base for a wide variety of dishes, such as stocks, soups, stews and sauces.
Similar flavor bases include the Italian soffritto, the Spanish sofrito, from Portuguese-speaking nations refogado (braised onions, garlic and tomato), the German Suppengrün (leeks, carrots and celeriac), the Polish włoszczyzna (leeks, carrots, celery root and parsley root), the U.S. Cajun and Creole holy trinity (onions, celery and bell peppers), the French duxelles (onions, shallots, mushrooms, sauteed in butter), and the Costa Rican olores (onions, celery, bell pepper and garlic).