While being interviewed by the Associated Press, Pennsylvania senator Rick Santorum condemned the right of two consenting adults to do privately whatever they pleased in the bedroom. This created an uproar in homosexual activist groups and praise from the far right. The scandal had mostly blown over until advice columnist Dan Savage took a suggestion from a reader to associate the senator's surname with a lewd sexual act. Dan Savage accepted the idea as long as it was an act that not just gay men could exclusively engage in, since Rick Santorum was saying how no one, gay or straight, had the right to private, consensual, sex. Readers of Dan's column submitted suggestions and voted on them. Some of the suggestions included having sex in public, being a new slang word for a condom, and having an orgasm induced by anal sex alone.
After counting the votes from his readers, Savage declared santorum to mean, "that frothy mix of lube and fecal matter that is sometimes the byproduct of anal sex." This had appeal because anyone could engage in anal sex to produce santorum, naming santorum after a sexual act itself might be a turnoff, and santorum is remarkably difficult to get off bedsheets.
The word appears to be spreading rapidly as many readers of the column have written about hearing it spontaneously. Even an English teacher in China has written in to tell how she taught the word to her class. Savage has had some luck with getting the word "pegging" adopted and appearing in sexual slang dictionaries, but it remains to be seen if santorum will stick.