The rule of thumb
My last post reprinted a ‘well I never’ e-mail containing no less than 22 supposed true facts, many of which are actually popular misconceptions. If you haven’t read it yet, go back and have a guess for yourself which ones you reckon will turn out to be untrue.
I’m going to go through them one by one looking at the evidence, starting with the purported origin of the phrase ‘rule of thumb’:
In the 1400’s a law was set forth that a man was not allowed to beat his wife with a stick thicker than his thumb. Hence we have “the rule of thumb”.
As with many popular misconceptions, a quick Google search is all it takes to cast doubt over this claim. The number one result, as with many searches nowadays, is a Wikipedia page, Rule of thumb. A section called origin of the term takes up the majority of the page, and no less than seven competing histories are listed. On the domestic violence theory, Wikipedia says:
Linguist Michael Quinion, citing the research of Sharon Fenick, notes that there are some examples of a related usage historically — most notably with regard to a supposed pronouncement by a British judge, Sir Francis Buller, that a man may legally beat his wife, provided that he used a stick no thicker than his thumb. However, it is questionable whether Buller ever made such a pronouncement and there is even less evidence that he phrased it as a “rule of thumb”; the rumoured statement was so unpopular that it caused him to be lambasted as “Judge Thumb” in a satirical James Gillray cartoon. According to Quinion, the term “Rule of Thumb” was first documented in English in 1692, long before Buller’s reported pronouncement. The first known usage of the phrase “rule of thumb” in direct reference to domestic violence was in 1976, in the book Battered Wives by Del Martin
There’s even a copy of the James Gillray cartoon, ‘Judge Thumb’, in which Judge Buller is depicted selling thumb-shaped sticks to wife-beaters in the street. Charming. Still, whilst the rule is mentioned, it’s never explicity referred to as the ‘rule of thumb’.
Another website, phrases.org, suggests that the judge may not even have made this ruling, referencing Edward Foss, who apparently wrote that “no substantial evidence has been found that he ever expressed so ungallant an opinion”.
Yet more attempted debunking comes from Trust Canlaw, who put it down, rather amusingly (and I suspect falsely) as ‘yet another feminist myth‘.
So there seems to be no evidence of a ‘1400’s law’. Even if there was, however, (and there does at least appear to have been the notion of such a law), this still wouldn’t be good evidence for the origin of the term. After all, such a rule could itself be based upon an already-existant phrase and idiom ‘the rule of thumb’.
If you stop and think about it, using a thumb as a basis for a rule, or rough guide, is perfectly natural, be it measuring, pointing or estimating distances or wind directions (all of which Wikipedia gives as possible origins). Each of these rules of thumb could have arisen independently, leading to the phrase being adopted as a more general idiom. We do, after all, have measurements derived from feet and hands. Fingers, paces and even arm spans.
None of these more natural explanations for the origins of the phrase are quite as interesting as the domestic violence one however, which comes across as more shocking and surprising, both qualities which can help a popular misconception spread.