probably originally a nonsense word, used in the phrase “You bet your sweet bippy!”, denoting an unspecified body part
The line “You bet your (sweet) bippy!” was popularized in the American television show Rowan & Martin’s Laugh-In, which ran from January 1968 to March 1973. George Schlatter, the executive producer of the show, said the following about the word: “Our shows are gone through quite thoroughly for taste. What upsets most of the critics are the jokes they don’t understand, and that’s more of an educational problem than a taste problem. We say things like ‘You bet your bippy!’ or ‘You bet your nurdle!’ I’m sure some people attach a dirty connotation to those words. We don’t even know what they mean; they’re just funny” (quoted in Joan Barthel, “Hilarious, Brash, Flat, Peppery, Repetitious, Topical and in Borderline Taste,” New York Times Magazine, 6 Oct. 1968). The hypothesis that the word was borrowed from Yiddish pipik/pupik “navel” has not been confirmed.