The word "胯下之辱" is formed by combining the characters 胯 (crotch), 下 (under), 之 (a possessive linker), and 辱 (humiliation), creating the literal meaning "humiliation under the crotch". It derives directly from a historical account where Han Xin endured shame by crawling between a bully's legs, thus the phrase encodes this event by using 之 to grammatically link the location 胯下 to the type of disgrace 辱, resulting in a fixed idiom denoting a severe personal insult.