means A path worn through wild or rough country, or the track or scent left behind by something that has passed.

from From Old French 'trailler,' to tow or drag, ultimately tied to Latin 'tragula,' a dragnet — a cousin of 'trawl.' The first trails were literally things dragged behind: the mark left in mud or grass by a hauled load, a tail, a hunted animal. Only later did the word turn around and name the path itself rather than the drag-mark on it.