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I think the problem is the dashboard was originally an optional panel seperating a buggy driver from the horse pulling it; preventing dirt from getting dash-ed on to them (from hooves; or horse-farts, I imagine). The part on a tram, between the driver and road, was also called a dashboard -- so it might have come to cars [automobiles] via trams or omnibuses?

Dashboards were kept, and as gauges fell into use the gauges were mounted on or about the dashboard. So the dashboard is the ancestor to the gauge display holder, and to the firewall.

Patent US652940 (1900) shows a water-level gauge mounted to a dashboard in a "Whitney motor wagon".