The image seems to be mixed, but there's no doubt so far that the examples we know of containing "bar" are significantly later than some of those containing "car". My guess would be that "bar" arose through an extension of the cock-fighting metaphor, and that your "spurs" came about similarly (many people won't even have known what a "car" was, but may well have been followers of cock-fights) but we can rarely be certain about such things.

Before we can consider this "version" you mention as potential evidence of anything, you'll need to say where you got it, from whom, and when; and, ideally, everything else you know about it.