The phrase "胡说八道" is formed through the historical blending of cultural and religious criticism. "胡说" (húshuō) originates from a dismissive ancient Chinese view of the "胡" (northern tribes), implying their speech was nonsensical or barbaric, while "八道" (bādào) refers to the Eightfold Path of Buddhism. The idiom thus metaphorically combines the idea of "wild talk from northern outsiders" with "deviations from the correct Buddhist doctrine", eventually merging into a single expression to vehemently label any speech as complete, unfounded nonsense.