whisper circuit
n. A form of rumor mill in which people trade gossip, innuendo, and other unsubstantiated data, particularly within the investment community.
Examples
1999
Meanwhile, Epinions.com has kept up constant reconnaissance on the competitors it will be jockeying with this fall, despite those competitors' best efforts to keep their strategies secret. The Valley has what it calls the "whisper circuit," which is not so much wild gossip as the ability to call in old favors and threaten to pull people's teeth. A lot of whisper-circuit surveillance leaks out the back door of companies through their engineers, who often refuse to lie on principle or are very bad at it when they try.
—Po Bronson, “Instant Company,” The New York Times, July 11, 1999
1981 (earliest)
Whoops, here goes another secret. The Anonymous Giver of that $209,508 red-and-gold-trimmed Lenox china to the White House is kind-hearted Mrs. Bob Vojvoda. Mrs. V., as we dub her on the Whisper Circuit, is comfily anonymous in St. Michael's, Md.
—“The Ear,” The Washington Post, October 07, 1981
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