In petanque, the word carreau refers to the perfect shot, when the thrown boule makes a direct hit on the target boule, knocking the target boule away and exactly taking its place.
Outside of petanque, in everyday French, un carreau means “a square”. It can also be used to refer to square things such as window panes and floor tiles. It can also by extension be used to refer to tiled floors and to floors in general. Laisser quelqu’un sur le carreau is to lay somebody out on the floor, to deck him.
Carreau can also refer to the diamonds in a deck of cards. Hence the name of the famous bronze boule from La Boule Intégrale, the AC (as de carreau, ace of diamonds).
Hence also the name of one of the designs in Obut’s old Tatou line of leisure boules— the “Card Carreau”.
What’s the connection between a floor tile and a petanque carreau ? You can find the answer in the collection of Petanque Terminology assembled by Jeff Widen.
The origin of the term is thought to have come from the fighting expression “rester carreau” – “to remain on the spot, to be laid out cold.” “Le carreau” means the “floor” (usually only applied to one that is either tiled or paved).
So when you rester carreau (“stay on the floor”) you drop to the floor like a rock and you stay there. Which is what a thrown petanque boule does when it makes a carreau.