The story
From dash (“to sprinkle; to splatter”) + board for meaning 1. Possibly expanded meaning later.
Etymology from Wiktionary, CC BY-SA 4.0.
dashboard
dash·boardToday it means: An upturned screen of wood or leather placed on the front of a horse-drawn carriage, sleigh or other vehicle that protected the driver from mud, debris, water and snow thrown up by the horse's hooves. Full definition →