Couillon - Cooyah/cuyoo

From: Li walon po tertos

Cooyah/cuyoo is definitely "coyon/couyon" in Walloon and it is also a card game here. The original meaning is "ball, testicle".
Apparently it was used to refer to the circle used in the calculation of the scores.
You can find more information in French here for instance:
https://reglesdejeux.github.io/regles-du-jeu-couillon/index.html

(If you use "couillon" in French, it actually means "idiot")

Here in Wisconsin the popular Belgian card game has been spelled a couple different ways. Pronounced "koo yo" here, sometimes with almost a Q sound at the beginning.