Most people outside the entertainment industry have probably only heard of "the greenroom" through guests' remarks on television talk shows.

For example, Tony Randall may say to Johnny Carson, "As I was listening to your monologue back in the greenroom it reminded me of . . . " or "We were talking back in the greenroom about. . . ."I don't remember Johnny ever asking Tony, or anyone else, to explain "greenroom," and I guess that's because the word belongs to a professional lingo that the regulars understand.

From such offhand comments, viewers at home may get a vague idea of a waiting room decorated in shades of green. Occasionally, during a studio tour, or when David Letterman goes backstage, followed by a cameraman, we may even get a glimpse of the greenroom itself.

But have you noticed that the greenroom is almost never green? I've been in dozens of greenrooms. Every TV studio has one, and many have a sign saying "Greenroom" on the door. But these rooms are never, as I recall, painted green.

For that reason I always ask a technician, a producer or a guide, "Why do you call this room the greenroom?"

"Oh," I've been told repeatedly, "that's because green is a very restful color."

When I point out that the room isn't green, they may say, "Well, it used to be green," or "The waiting room in our old studio was painted green, so we still call it that."

If green is such a restful hue, I wonder why more greenrooms aren't repainted. Maybe institutional beige, the usual waiting-room color, is also a very restful color.

Veteran television pros may tell a different story, such as, "Calling this the greenroom is an old theatrical tradition." Some TV folk say that a famous London theater originally had a green waiting room, but they're never sure exactly which theater it was.

Hearing these greenroom tales, I did what any English professor would do - I looked up the word in the Oxford English Dictionary (OED). I found 10 quotations, the earliest being from the year 1701:

"I do know London pretty well, and the Side-box, Sir, and behind the Scenes; ay, and the Green-Room, and all the Girls and Women-Actresses there."

Another quotation from England, dated 1736, described "most of the players drinking tea in the Green-room." Nowadays, the waiting-room scene is similar, but with coffee and soft drinks added to the menu.

In 1823 the American author Washington Irving described one of his characters as "a green-room veteran (who has) written for the London theatre." The OED also quotes an 1887 reference to "actors' gossip and green-room whispers."

When I showed these "greenroom" references to my wife, she said, "Why isn't Jane Austen's use of the word listed?"

Then she got out her well-read copy of Austen's 1814 novel "Mansfield Park" and found the passage in which a group of young people plan an amateur home theatrical. One of them says, "And my father's room will be an excellent green-room."

So "greenroom" (the word "green-room" later lost its hyphen) has a history, but where did the word originate? There are several theories, but none has been proven, as columnist William Safire learned when he wrote a New York Times column about the greenroom, which was so named, he assumed, because of "the guest-relaxing color on its walls."

One reader assured Safire that the stage waiting area was originally called the "attiring room" or "tiring room," until shrubbery for stage decoration was stored in one. Then it became known as the "greens room" and later the "green-room."

Another reader wrote to Safire saying that green cloth was so widely used on the curtains, costumes and audience seats in English theaters that it became associated with every part of the building.

Other explanations, though plausible, were equally unverifiable, and Safire was forced to conclude that "the reason for the name remains obscure."

The suggested etymology in the OED is short, sweet and just as vague as any other I've seen. The dictionary says that the greenroom is "probably so called because it was originally painted green."

I suspect that's as close as we'll get to explaining these greenroom tales.