'heretical' originates from Medieval Latin, specifically the word 'haereticus'/'haereticalis', where the Greek root 'hairein' meant 'to choose'.

'heretical' changed from Late Latin 'haereticus' and Old French 'heretique' and eventually became the modern English word 'heretical' via Middle English.

Initially it referred to matters relating to a 'choice' or to a member of a sect ('one who chooses' a different belief), but over time it evolved into the current meaning of 'holding beliefs contrary to established doctrine'.