What does “panneau” mean in French?

Un panneau is a sign: the green motorway boards, the red stop, the blue plate with the town name on it. It is also the panel sense — un panneau solaire is a solar panel, un panneau d’affichage a notice board. One word covers both the thing you read and the flat surface it sits on, which is why it turns up constantly in directions, on roads and in DIY.

The word goes back to Latin pannus, “cloth.” In medieval hunting a panneau was a stretched net for trapping game, and that is where tomber dans le panneau comes from — literally “to fall into the net,” now “to fall for it.” Road signs kept the flat-surface sense; the idiom kept the trap.