Look, if I’m going to use this tag to collect this series, it makes sense to take a look at the origin of this phrase. It’s a favorite for highlighting the risks of defaulting to inherited grammar rules without understanding how they’ve been set in the first place or whether the story you’re told has any veracity.
Apocryphal stories tell of an 18th century ruling and its impact on contemporary pop media. Or was it the 1650s? Or maybe it was the 15th century? Or maybe this is an invention of second wave feminists in the 1970s? Coming up in the late 20th century, I was certainly taught that it comes from an archaic rule allowing a man to beat his wife as long as the switch was no thicker than a thumb (his thumb? hers? the magistrate’s? the details have always been unclear to me)–but the existence of such a ruling is mostly described as a rumor in even semi-reliable sources.
The OED suggests the term is instead one of those delightful non-standard imperial measurements. Where a foot measures an appreciable distance, a thumb was used for things like baking or brewing. Given the smaller relative sizes (and thus larger relative errors), it makes sense that this method of measuring has become a byword for measurement-by-experience rather than measurement-by-precision.
Here’s the rub, though. There are so many English-speaking audiences that have internalized the alternative narrative of misogyny, that the phrase could be risky to use in professional settings–unless you’re ready to deal with uncomfortable jokes about beating wives. And the extra salt in the wound? English is a language relying on an unfair share of idiom and rule-of-thumb guidance. That tendency to use experience rather than a shared, standardized rulebook has led to a language full of pitfalls and extra considerations that’s challenging even as a first language to learn.
Something Polished 