'caustical' originates from Latin, specifically the word 'causticus', ultimately from Greek 'kaustikos', where the root 'kaiein' meant 'to burn'.

'caustical' changed from Latin 'causticus' and Greek 'kaustikos' into Middle French forms and Middle English 'caustic', eventually producing the adjective form 'caustical' in older English usage.

Initially, it meant 'related to burning or able to burn', and over time it also developed the figurative meaning of 'bitingly sarcastic; sharply critical', which it retains today.