Where does rule of thumb come from? The idiom referring to a practical measure based on experience was never actually a law, though it does pop up in legal opinions suggesting that it’d be okay to let a man beat his wife if the stick was less than a thumb in width. This is part of a complete episode.
Transcript of “Rule of Thumb Origin”
Hello, you have A Way with Words.
Hello.
Hi, who’s this?
This is Linda Oestreich from La Mesa.
Hi, Linda. Welcome to the program.
Hi, Linda.
Well, I do a little teaching on the side at UCSD Extension, and my students brought up something that I went out and Googled, and then I couldn’t find one answer, and that was the origin of the phrase, a rule of thumb.
Aha. Okay. What did they heard?
Well, the two very different places were, one, which is the one I thought it was, was it had something to do with carpenters and measuring and approximately an inch from your thumb joint to the tip. I also found some stuff that talked about the width of your thumb for carpenters, but then the one that really made us talk was the fact that there was actually supposedly some old trial data that talks about men were not able to beat their wives with a stick any wider or thicker than their thumb. I could not really find a definitive answer online. And I thought, well, the best thing to do is go to Martha and Grant and see what they say.
So your question really has two parts. And one of the parts is about the etymology of the rule of thumb itself. When you talk about a rule of thumb, what you’re talking about is a practical measure sort of based on experience, an informal guideline, that kind of thing, right?
Correct. As a rule of thumb. And as far as we know, there was never actually a law on the books passed in English law that said that. But there have been legal opinions where judges have mentioned things like there was a judge in the 1780s who wrote a legal opinion saying that that was a good idea to let a man beat a wife as long as his stick was less than a thumb in width. And that may have reflected an idea floating around at the time. But the expression of rule of thumb had been in use at least 100 years before that in exactly the kind of way you’re talking about as a unit of measure when you’re, you know, building something, carpenter, measuring cloth. Literally putting your thumb up against something as a guide.
Yeah. And was it from the joint to the tip or was it the width across? Because I did find both of those as well when I did my Googling.
Oh, that’s an interesting question. Maybe either way, right?
Yeah, maybe either way. I think it’s the joint to the tip, though. That’s what I had always thought until, like I said, this just recently came up. And it was, I found it interesting because we had started the discussion in a completely different place. And this is a discussion board, you know, so you don’t have quite the interaction as you do in a face-to-face class. But even so, it was nice to get off track and onto something kind of fun.
This is one of those folk etymologies that won’t die, though. The rule of thumb doesn’t come from a law. There never was a law. There were some judicial decisions, but there was never a law.
Yeah, I mean, the fact is that the courts haven’t always been friends of victims of domestic violence. There was the Joyner v. Joyner case in 1862, which is really worth reading. It’s a divorce case, and the judicial ruling there was that there are circumstances under which a husband may strike his wife with a horse whip or may strike her several times with a switch so hard as to leave marks on her person. But that’s not enough grounds for divorce.
But the rule of thumb expression, the idiom, existed long before that. There’s no sourcing there to the rules.
Yeah, no cause and effect there in terms of the etymology. But unfortunately, this is one of the things that won’t die. And every time you use rule of thumb, you are at risk of somebody leaping out and saying, you’re sexist.
But they’re wrong.
Exactly.
They’re wrong.
Well, good. I’m glad to hear that. I’ll go back to what I had remembered and learned from many years ago myself. And, you know, like I said, this new thing, it really was new for me. And as the instructor, you know, I’m supposed to know everything.
Yeah.
Well, definitely worth discussing. I mean, domestic violence.
Yeah.
Or at least have better contacts like Martha and Grant as the instructor, right?
Absolutely.
I will be sharing this.
Okie doke.
Okay.
Well, thank you so much, Linda.
You’re very welcome.
Bye-bye.
Thank you.
Bye-bye.
