A surface showing many measures at once. It exists to make a state graspable in a glance.
English compound of dash (Middle English daschen, to strike violently) + board (Old English bord, plank); originally the board on a carriage that stopped mud being dashed up at the driver, later the instrument panel showing a system's state at a glance.
The oldest dashboard kept mud off a driver, not information in front of one; the instrument-panel sense is a later, unrelated life for the same board. What survived across both lives is the position: something mounted directly in the line of sight.