The phrase in French is femmes d'une certaine age. The term, however, can apply to either sex. Without the certain, the phrase un homme d'un age translates literally as "a man of an age" and is defined in the Oxford-Hachette French Dictionary as "a man of advanced years."

And now to the point: is that certain age getting older?

"When I wrote the book in 1979," Dr. Rubin says, "the 'women of a certain age' were in their late 30's and early 40's. I think that has changed with the baby boomers and the lengthening of the life span. I'd say the 'certain age' has now moved to the age of 50 or 55."

Look at it this way: late 30's or early 40's is no longer that "certain" age; it's moved up a decade. The good news is that 40 is still young, at least linguistically. That's how it seems to a language maven of a certain weight and getting long in the tooth.

Which brings us to long in the tooth, which I used in a political column in an unkind reference to vigorous Senator Bob Dole. (The first user was William Makepeace Thackeray in an 1852 novel: "She was lean, and yellow, and long in the tooth; all the red and white in all the toyshops of London could not make a beauty of her.") In my piece, I was impelled by wordmavenhood to give the derivation of the expression: "As horses age, their gums recede, making their teeth appear longer." My source was the Oxford English Dictionary: "displaying the roots of the teeth owing to the recession of the gums with increasing age; hence gen., old."

This folk wisdom about the illusion of tooth-lengthening was promptly challenged by Michael Brisbane McCrary, former Hong Kong polo player and now a squire in Hunter, N.Y.: "Horses actually do get 'long in the tooth.' It is not receding gums; their teeth continue to grow out (like beavers, and there is a word for it beginning with 'ex-') throughout their lives until the teeth actually fall out."

Mr. McCrary (his wife is Jane Buckle; her long-panted-for book, "How to Massage Your Dog," is scheduled for publication this fall) continues: "The growth of the horses' teeth is required because they would wear down in the process of eating in a natural setting. As the teeth grow out, lines show; this is how one usually tells the age of a horse. And this is the background to the phrase 'Don't look a gift horse in the mouth'; i.e., if it is a gift, don't ask how old it is."

That moved me to call the National Zoo. I don't call the Bronx Zoo anymore; any zoo that calls itself a "wildlife center" cannot be trusted. (A spokesman at our national zoological park, Mike Morgan, remembered me as the one who revealed the reason that pandas have reduplicating names like Ling-Ling and Hsing-Hsing they can't hear well and zoo keepers have to call them twice.)