I honestly don’t know of a single word in Irish English that would name this. If I had to give someone directions to follow this, I’d probably describe it rather than name it, e.g. “a faint path” or “a barely visible trail”. Which actually fits fairly well with tagging it highway=path, trail_visibility_bad.
I certainly wouldn’t use “track” for a way that doesn’t allow some form of 4-wheel vehicle access (or at least look like it once did).