You may notice Flynn hyphenates the term (scot-free), while in the book it is not hyphenated. It turns out that there is no clear preference in edited work to hyphenate or not; this is a case where it can go either way. However, if you go by Webster’s, you will find it hyphenated.
Here is the entry from the book:
Scotch free/scot free
Getting away with something “scot free” has nothing to do with the Scots (or Scotch). The scot was a medieval tax; if you evaded paying it you got off scot free. Some people wrongly suppose this phrase alludes to Dred Scott, the American slave who unsuccessfully sued for his freedom. The phrase is “scot free”: no H, one T.
Further down in her article, Flynn notes that Jeremy Fowler of Fowler's Dictionary of Modern English Usage has called this a “special kind of eponym eggcorn,” but when Flynn identifies an eggcorn as “a language error when someone’s usage is close but not quite correct,” she is off the mark. An eggcorn springs from a misunderstanding of the origin of a word or phrase, such as the ubiquitous “for all intensive purposes” in place of “for all intents and purposes,” where the user mishears the phrase and creates a different meaning, in this case believing purposes must somehow be intensive. An error like Trump’s is more like a plain old homonym error, or if you like, a special kind of eponym homonym.
If only Flynn had chosen to cite another book that is on sale this month:
. . . which features an “eggcorn” right on the cover, and has all the information you would ever need to help you define the term to perfection every time!
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