The word 神经病 is formed by combining three characters: 神 (shén), which originally referred to spirits or the mind; 经 (jīng), meaning channels or pathways; and 病 (bìng), meaning sickness or disease. Together, they conceptually create the idea of a "disease of the nerve pathways", metaphorically extending from a literal medical term for neurological disorders to a common, though offensive, colloquial expression for someone perceived as acting irrationally or crazily, implying their mental "wiring" is ill.