idiom. When sphincters clench in a most holy fashion, this expression is recommended, though not endorsed by any church.
Real citation: "A Jesus-freaky group known as "The Resistance" have their Bibles in a knot over Jessica Simpson's "slutty" performance in her music video remake of "These Boots are Made for Walking." Simpson is seen wearing the devil's hot pants, as well as washing the devil's hot rod while wearing the devil's skimpy bikini--which makes Resistance rep John Conner hotter than Hades. "It's sad to see [Jessica] whore herself out like this. She's a singing stripper!" Now hold on there, John! Who ever said she could sing?"
(Ann Romano, "The Week in Review," June 27, 2005, The Portland Mercury, http://www.portlandmercury.com/current/one_day.html)
Made-up citation: “I’ve never gotten my knickers in a twist, and I’ve never gotten my bibles in a knot, and I’ve rarely gotten my panties in a bundle. However, I frequently get my thong in a bunch.”