Creole style “Holy Trinity” is onions, bell pepper, and celery. My first big recipe book was by Chef Prudhomme, cooked a lot of things in that book. Almost all of them started out with sauteing those veggies and than making a roux, Cajun napalm.

As a guy who was limited on cookware. Everything ends up in a big ass pot was very appealing.

I’ve only ever heard that term used in Cajun cooking, where it refers to onion, celery, and bell pepper.

The version with carrot is mirepoix.