I am English that has never been true though that was a theory it has been proved wrong as it has never been ok to beat a woman and one of the punishments for domestic abuse was to go though the ordeal of pots and pans where the town’s people would parade the man though the street banging pots and pans together so that all the town knew that the man was a woman beater.
I thought rule of thumb was essentially that exact definition but meant for catholic school teachers, they could hit kids with a ruler (or earlier known as just a "rule") no wider than their thumb
i actually remember the origin of the rule from the opening of the boondock saints from i think the meat plant scene wow i usually don't comment here on RT but i guess replay if y'all thought the same thing as well.