'crazier' is the comparative form of 'crazy', which originates from Middle English, specifically the word 'craze', where it meant 'to shatter or break'.

'craze' in Middle English evolved into 'crazy' in modern English, and 'crazier' is formed by adding the comparative suffix '-er'.

Initially, 'crazy' meant 'full of cracks' or 'broken', but over time it evolved into its current meaning of 'insane' or 'wild'.