A character hears something that ends up Squicking the hell out of them. Such as the sex lives of people they desperately try not to think about in the same sentence as the word "sex", such as parents or grandparents. Other bodily functions are the other most common variant, such as anything to do with bowel movements or a woman's menstrual cycle. Especially while the speakee is eating.
Named [...] [tvtropes.org]