Puritan
n//ˈpjɔːɹɪtən//puritan, puritansk
A member of a particular Protestant religious sect advocating greater purity and piety.
(usually, derogative) Acting or behaving according to the Puritan morals (e.g. propagating modesty), especially with regard to pleasure, nudity and sex; ascetic.
(usually, derogative) A puritanical person.