When I came across this definition, from the website Word of the Week, I figured other readers would be as surprised as I was to know it has nothing to do with Scots, or Scotch, at all, despite the common assumption otherwise. The term does pop up occasionally in law talk, usually in the derisive sense, as in “The scumbag got off scot-free.” That sense, at least, makes some etymologic sense.
“scot-free (adj.) Old English scotfreo “exempt from royal tax,” from scot “royal tax,” from Old Norse skot “contribution,” literally “a shooting, shot; thing shot, missile,” from Proto-Indo-European *skeud- “to shoot, chase, throw” (see shoot (v.); the Old Norse verb form, skjota, has a secondary sense of “transfer to another; pay”) + freo (see free (adj.)). First element related to Old English sceotan “to pay, contribute,” Dutch schot, German Schoß “tax, contribution.” French écot “share” (Old French escot) is from Germanic. (thanks to etymonline.com)”
So now you know what I know, plus what you know, which makes you smarter.