'puritanical' originates from English, specifically from the noun 'Puritan' combined with the adjectival suffix '-ical'; 'Puritan' refers to a member of the Puritan movement.

'Puritan' entered English from post-classical Latin 'puritanus' (related to Latin 'puritas' meaning 'purity') via Middle English and early modern English; the adjective 'puritanical' developed later by adding the suffix '-ical' to form a word meaning 'of or like Puritans' and then broadened to mean 'excessively strict morally'.

Initially, it meant 'relating to the Puritans (the religious group)'; over time it evolved into the current sense of 'excessively strict in moral or religious matters'.