I can't comment on the history of the act, but I recall very specifically when the term "pegging" was coined, and it just barely squeaks past the 20-year rule, I believe.

In the April 19, 2001 Savage Love sexual advice column, Dan Savage posted the following letter from a reader:

Probably my favorite sex act is to be fucked by a woman wearing a strap-on. Every other sex act under the sun, from blowjobs to facials to scat, has a catchy one-word name--but not a man getting fucked in the ass by a woman wearing a strap-on. Could you come up with a name for this activity, if only for the sake of those of us who place ads in the personals?

Straight Boys Have Prostates Too

In his response, he said he didn't know of any prior term, which given his prominence (he was nationally syndicated in alt-weekly papers) and vocation, suggests there wasn't one in widespread currency in America at the time.

In his response, he invited readers to come up with a new term for the purpose:

I was unable to come up with a single word that adequately captured the patriarchy-shattering nuances of a woman fucking a man in the ass with a strap-on. Hopefully someone out there reading this--anyone know where Rich Hall is these days?--can help you out, SBHPT.

It proved to be a popular request, and readers started sending in suggestions. Savage devoted his May 24, 2001 column entirely to the topic. He chose three contenders, "punt", "bob", and "peg", and set up a voting system for readers.

In his June 21, 2001 column, he announced that 12,103 votes had been cast, and the winner was "peg".