The Merriam-Webster dictionary Twitter account corrected the President of the United States this morning:
📈'Scot-free': completely free from obligation, harm, or penalty— Merriam-Webster (@MerriamWebster) December 3, 2018
'Scott Free': some guy, probablyhttps://t.co/nQFL7I0ELH
It occurred to me that I had no idea why something might be scot free specifically, and I surmised that it might well be an ethnic slur, the stereotype of the miserly Scotsman being what it is. To the OED, then!
And the OED informs us that a scot (noun two) is a sort of tax or duty, and by that in later use the charge or amount to be paid, esp. at a tavern or for entertainment. Thus, if you don’t have to pay your scot, your entertainment is scot-free. So that’s clear enough. But the scot of this meaning is not connected at all to the Scots of Scotland, at least in terms of their etymological derivation. In fact, the OED claims that scot-free is a variant of shot-free, for the use of shot that is a payment or share, as in (they say) to stand shot or pay for a round of drinks. I have never heard that usage, but then I don’t hang around in bars or pubs very much. Still, it’s good to know that in going scot-free, one would not be throwing away one’s shot.