The word "疯疯癫癫" is formed through the process of reduplication, specifically the AABB pattern, where the disyllabic adjective "疯癫" (fēngdiān, meaning "insane" or "crazy") is duplicated. Each character is repeated individually ("疯" becomes "疯疯" and "癫" becomes "癫癫"), then combined. This grammatical construction intensifies the original meaning, transforming it from a state of mental derangement into a more vivid and often colloquial description of wildly erratic, foolish, or unrestrained behavior, conveying a sense of continuous or exaggerated madness.