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Just a comment, but I find automobile electrical terminology really confusing.
We refer to earth or ground, but it it isn’t really.
All we have is a DC circuit with a positive and negative.
There is no earth as such in a DC circuit.
I think most people think of the earth as it is in an AC circuit.

The terminology I think must be lost in the mists of time. Rolling Eyes

Yes, indeed While earth and ground have the same historical background (sticking a metal bar in the mud and using it as return channel for telegraph signals), in electrical/electronics engineering we usually use earth only when talking about AC.
ground is used with DC to refer to the common point all voltages in a circuit are measured against - it's considered zero. But isn't there a difference between using "earthed" and "grounded" in British and American English?
The German term for ground is "Masse" (mass), by the way. It's easier to mentally connect this term to the metal "mass" of a chassis, for example. Also its symbol is a thick horizontal bar, while earth has three thin bars (thinking of soft soil).
Why don't we say "negative"? Maybe because in electronics the zero-Volt reference doesn't need to be at the negative pole of a voltage source. By definition it can be anywhere in a circuit, resulting in negative voltages relative to that zero (still with me? )