The weird thing is that based on the length of the wire and the size of the terminal it does not look like it is meant to hook directly to a battery. Is there something else in the compartment that is within reach of the wire and the right size post for the terminal? What about empty screw holes where something like a breaker or switch used to be installed but is gone now? As to tracing the wire, first I would just visually try to see where a wire the same size and color jumps out of the harness, or at your main panel, before you start untaping things and pulling wire loom apart. If you are not sure if you found the right wire you can disconnect the other end and check with an ohm meter.
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