Gracious, Emily, you’re glowing like a pig.

Dear Word Detective: My daughter’s teacher told her that “sweat” should only be used for animals, and that humans “perspire.” I think that this is just an urban legend and that it is quite correct to say that a person “sweats.” Am I right? — Suressh.

Say, could you do me a favor? Please ask your daughter’s teacher if I can borrow that time machine for a moment. I need to zip back a few decades and change my college major. I figure dual law and medical degrees would stand me in good stead, although with my luck I’d probably just end up suing myself. But it would still beat journalism and animal husbandry, or whatever it was I took. Things were kind of hazy back then.

The reason I mention time travel is that your daughter’s teacher appears to be recycling a bit of faux-Victorian vocabulary guidance, the most common version of which goes: “Horses sweat, men perspire, women glow.” I say “faux-Victorian” because I cannot actually find the axiom in print before the 1950s, but in any case, it seems to have been a staple of etiquette manuals for many years, so apparently at least some people took it seriously. On the other hand, neither “sweat” nor “perspire” are listed in the Oxford English Dictionary as synonyms of “glow,” so it’s unlikely that “glow” ever led an independent existence as a euphemism for “sweat” outside of that particular adage.

The goal of “Horses sweat, men perspire, women glow” was, of course, to encourage the use of “glow” as a more refined word than “sweat” or even, in that more delicate age, “perspire.” There’s nothing really wrong with either “sweat” (from the Old English “swat”) or “perspire” (from the Latin “per spirare,” meaning “to breathe through,” in this case referring to “vapors” escaping the skin). In fact, the root “spirare” in “perspire” also gave us the word “spirit” (as in “the breath of life” or soul), so “perspire” actually has a fairly ethereal pedigree.

“Perspire” is, however, usually considered a more refined word than “sweat,” which is certainly worth knowing. That distinction is, of course, entirely arbitrary from a linguistic standpoint, but English has a long history of granting Latinate (or Anglo-French) forms higher social status than Anglo-Saxon words. Many of the words we use for livestock (“cow,” “pig,” “sheep,” etc.), for example, are short, blunt Anglo-Saxonisms of the sort used by medieval peasants, while the names of the finished products (“veal,” “beef,” “mutton,” “pork,” etc.) are rooted in the Anglo-French of the gentry who could actually afford the meat.

Stand back.

Dear Word Detective: I’ve written a play that takes place in 1880, and the linguists in my life insist that the phrase “pent up” is a twentieth century phrase. I cannot imagine an audience member throwing his hands up in disgust and storming out of the theater the instant he heard the Victorian-garbed actor utter the phrase “pent up,” but for the sake of accuracy, does that phrase belong in my 1880 play? — Daniel Tobias.

Oh goody, another theatrical anachronism question. I actually get quite a few of these from playwrights and screenwriters striving to avoid those “Julius Caesar glanced impatiently at his wristwatch” moments that reviewers love to mock. In fact, I usually answer such questions by email even when I don’t use them in a column, and I like to think I’m single-handedly keeping both Hollywood and the American theater world on an even keel, historical-accuracy-wise. Yes, I like to think that, despite voluminous evidence to the contrary. The least they could do is pay attention to my warnings about Ralph Fiennes. I still can’t believe I sat through The English Patient.

Not to devalue my own role in your play, but I too tend to doubt that today’s theatergoers are likely to freak out and start throwing rotten vegetables upon encountering one little anachronism. But one never knows when the audience may contain a disgruntled etymologist with a short fuse (don’t laugh, I know a few), so here goes.

The good news is that your linguist friends are wrong, and apparently lazy to boot, because even a cursory glance at the Oxford English Dictionary (OED) acquits “pent up” of being absent for the 19th century. As a matter of fact, the first printed appearance of “pent up” in the modern figurative sense of “held in or back under pressure” (OED) found so far dates back to the 17th century (“Whil’st boyling rage (pent up) last high did swell,” William Alexander, 1637). That’s a pretty good cushion against a charge of anachronism.

The literal sense of “pent up” when it appeared earlier, in the 16th century, was “confining,” as in a small room. Interestingly, “pent up” apparently arose as an emphatic form of the adjective “pent,” meaning “closely confined” or “held back under pressure.” This “pent” was actually the past participle of the verb “to pend,” which itself was a form of “to pen,” which meant to confine something or someone in an actual pen or cage.