Mirepoix (cuisine)
Similar flavour bases include the Italian "soffritto", the Spanish "sofrito", "refogado/sufrito" (braised onions, garlic and tomato) from Portuguese-speaking nations, the German "suppengrün" (leeks, carrots and celeriac), the Polish "włoszczyzna" (leeks, carrots, celery root and parsley root), the US Cajun / Creole holy trinity (onions, celery and bell peppers), and possibly the French "duxelles" (mushrooms and often onion or shallot and herbs, reduced to a paste).
Trois coups
This tradition, especially in France, may come from the Middle Ages, where three blows, symbolizing the Trinity, ended the mystery. These three blows could be preceded by eleven hammered ones (the twelve Apostles minus Judas). They may also be a tribute to the nine muses of ancient Greece. Hence, there would be nine rapid blows plus the "trois coups", thus twelve blows. Twelve, being a perfect number in its symbolism, symbolized the unity of theatre.