Courtesy of Avon Books

Sarah MacLean‘s new instant bestseller, “No Good Duke Goes Unpunished,” opens with this strikingly unsubtle line: “He woke with a splitting head and a hard [barnyard fowl].”

I happened to mention that opening line to Fordham University English professor Mary Bly, who writes wildly popular romance novels of her own under the name Eloisa James. Up till now, in her many bestsellers, Bly has resisted that particular word for the male sex organ, but that’s about to change.

“I just used [barnyard fowl] in my first book ever,” she crows. (You’ll see it in “Three Weeks with Lady X” this March.)

For Bly, it was a matter of staying abreast of the times. “I decided that I could either wither like a dinosaur or try to capture the rhythm of the way young women are speaking and thinking now,” she says. “So my mother is turning (yet again) in her grave!”

How did we get here?

Lee Siegel asked that question this weekend in an essay he wrote for the Wall Street Journal called “America the Vulgar: Whatever happened to the subtle thrill of real transgression?”

“Everybody is walking around sounding like Howard Stern,” Siegel wrote.

My new favorite expert on obscenity is Melissa Mohr, the author of “Holy Sh*t: A Brief History of Swearing,”  which came out this year from Oxford University Press. (You can hear her on this hilarious episode of the linguistics podcast Lexicon Valley.) With her PhD in English from Stanford University, she is perhaps the only woman in the world I can call up on the phone out of the blue to ask about the word [barnyard fowl].

Courtesy of Oxford University Press.

“Oh, that’s very interesting,” she says in her laughter-filled voice. “It’s a word used much more in Britain than in the U.S., where it became incredibly taboo, of course. But in Britain they still use the word for ‘watercock’ and ‘roosters’.”

After a quick trip to the Oxford English Dictionary, she tells me: “The first obscene use is in 1618, and it’s way down at meaning No. 20. But there’s also this amazing 15th-century lyric poem. Some scholars says it’s not a description of a penis, but it must be!”

She reads it to me. I take her off speaker-phone.

Mohr says the word was not tremendously common “until Victorian pornography — then it’s used quite a lot. But I suppose because romance novels are written for women, that word would have been seen as kind of masculine, kind of harder, and so previously, romance novels would have used other words.”

Bly’s editor, Carrie Feron, tells me, “Some romance authors use euphemisms, while others are more graphic.” A senior vice president executive editor at William Morrow, Feron has been editing some of the biggest names in romance since 1987, and she’s seen tremendous changes. “Years ago the books were ‘clean,’ meaning ‘no sex.’ I remember reading Kathleen Woodiwiss books and being mystified by what was going on (I was 12). And those were supposed to be the first explicit romance novels.”

In the Olden Days of Georgette Heyer, writers alluded to a gentleman’s [barnyard fowl] only in the most oblique terms. Feron says, “Years later when I worked in category romance, there was a lot of substituting of words. Euphemisms like ‘globes’ instead of ‘breast.’ It always sounded a little odd to me, but that was a while ago. Time moves on. I think it’s really hard to shock readers these days, especially after ‘Fifty Shades’ — which is not a romance — has become so mainstream.”

Curiously, Feron confesses that she doesn’t fiddle with the love scenes of books she’s editing: “I feel that if everything else in the novel is working — motivation, character, logic — authors should be allowed to write the naughty bits any way they like as long as it doesn’t make me burst out laughing.”

As Cole Porter noted way back in 1934:

Good authors too who once knew better words,

Now only use four letter words

Writing prose, Anything Goes.