means A flat, usually rectangular section of a surface, board, or material — or a group of people convened to discuss, judge, or decide something.

from From Old French 'panel,' meaning a piece of cloth or a small pad, which came from Latin 'pannus,' meaning 'a cloth' (the same root that gives us 'pane'). The leap from fabric to furniture and committees ran through the 'small piece' idea: a panel was once a literal scrap, then a flat section set into a door or wall, then — in legal use — a slip of parchment listing jurors, and from that list the 'panel' became the group of people themselves.