When I was in graduate school, I worked as a teaching assistant, and UCSB offered many one and two day courses aimed at helping the teaching assistants learn to teach and communicate with students. One of these courses was named "Feminist Pedagogy" and was required by one of the departments for which I worked.
By and large the course was a fairly useful run-through of the sorts of things that instructors often do that may upset or turn-off female students, and I had no problem with this.
However, there was a fair amount of time spent on the origins of common phrases, and how their origins might be offensive to female students. The problem, however, is that the origins discussed by the instructor were wrong. Dead wrong. Completely wrong.
The two examples given were "more bang for the buck" and "rule of thumb."
The phrase "more bang for the buck" comes out of military and political circles, where it meant more firepower for the amount of money spent. There is one other possible origin, however, that it comes from the explosives and mining industry, where it referred to the amount of explosive power per unit of explosive purchased.
The instructor, however, was convinced that it came out of prostitution, and referred to the tendency for men who solicit prostitutes to hire those who would work for longer, or be more exciting, I suppose. Really, I'm entirely unclear as to how, even assuming that the term "bang" to refer to sexual intercourse is old enough to pre-date this saying (it may be, I don't know), one would get "more" bang for one's buck with a prostitute...but, then, I have never solicited a prostitute, so what the hell do I know.
It is ironic that the misogynist false origin is the one that stuck with a group of self-described liberal people, while the possible actual origin involving warfare didn't. Both appeal to their sensibilities, but one actually makes some degree of sense (clue: it's not the false one).
Then, there's the phrase "Rule of Thumb" which, thanks to a particularly stupid list of false origins for common sayings that made email inbox rounds circa 1998, people think comes from a law that described the width of a rod with which a man could beat his wife. This is, however, not the origin of the saying at all. The origin is somewhat murky, but appears to come from the world of measurement and not domestic violence. In fact, there's evidence that it is a very old saying and well-predates both modern English and the legal codes that people often claim it is derived from. Given the way that the phrase is used - meaning a quick-and-easy way to reach a conclusion or course of action - having an origin in measurements makes significantly more sense than it having an origin as a way to determine the size of the cudgel that one might use against one's spouse.
But since then I have been thinking about this. While the erroneous belief about the origins of the saying "more bang for the buck" aren't particularly widespread, there are probably as many people who falsely believe that they know the origins of the saying "rule of thumb" as people who don't. Many, though not all, of these people refrain from using the phrase because of its allegedly sordid past. The problem is, since it doesn't actually have a sordid past, we are creating one, and therefore feeding some dubious notions about our ancestors. Moreover, we are casting the women of the past into the role of helpless victims rather than dealing with messier and more realistic views of women in the past.
In short, by buying into these false origins for these phrases, by trying to cast them in the role of remnants of a misogynistic past, the instructor for the Feminist Pedagogy course ironically bought into a misogynistic "men are the victors, women the victims" view of history and of our language, reinforcing the very "men vs. women" binary that most feminists admirably fight against - indeed most of this instructors statements and attitudes indicated that she did. So it was rather odd that she should so easily fall into this trap with this portion of her lecture.
The simple fact of the matter is that history is messy. Our ancestors did things of which we have every right to be proud, but they also did things of which all who are decent among us will be ashamed. I am not sure whether the ease with which we buy into the notion that our ancestors were so despicable comes from our desire to see ourselves as enlightened and better than them, or whether it comes out of a certain type of cultural self-loathing that many of us seem to have developed to a high degree.
Regardless of the source, it's pretty damn annoying, and likely counter-productive.
For other common sayings and practices that most people know false origins for, go here.