folk-etymologies or idiom, idem, idem

Via the resplendent rodeo of interesting things the Browser, here is a really fascinating list of English word pairs that are false cognates, seemingly related or organic extensions of the meaning, but are far from it, by Arika Okrent, who often writes for Mental Floss.
All of the entries are pretty surprising, and among my favourites was how shame-faced began as shamefast (like steadfast) as in being shamed into staying in one’s place and how something as innocuous, mildly irritating and apparently straightforward like the term hang-nail, obviously referring to the bits of skin dangling off one’s cuticle, actually has a more complicated etymology, reaching back to the Germanic root ang (as in anger) for something vexing and nightmarish. Though probably going out of my element, however, I do have to take exception with one anecdote: while indeed the phrase has nothing to do with Scotland or the Scots, I believe that to get off scot-free refers to medieval times tax-avoidance, when a subject managed to withhold some otherwise taxable asset (sceot) from his liege.