Wow. I love old commercials!!
And origins of sayings! Oh what fun! ;)
An old Benjamin Franklink story tells about how a young Franklin was approached by a fellow who stopped to admire the family grindstone. Asking to be shown how it worked, the stranger offered young Ben an ax, with which to demonstrate. Once his ax was sharp, the fellow walked off laughing, a newly sharpened ax in his possession. Thus, anyone with a hidden motive has an ax to grind.