Both Uses

Puritans
in
1984, by Orwell
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The sexual puritanism of the Party was not imposed upon them.†
p. 72.2 *

Puritanism = a religious movement of the 16th and 17th centuries to purify Protestant Christianity of rituals of the Catholic Church
Unlike Winston, she had grasped the inner meaning of the Party's sexual puritanism.†
p. 132.9

Definitions:

(1) (Puritans)
English Protestants in the 16th and 17th centuries who wanted simpler, “purer” worship and emphasized hard work over pleasure

Protestants are Christian groups that broke away from the Catholic Church; in the United States, well-known Protestant churches include Baptists, Methodists, Presbyterians, and Episcopalians.
(2) (meaning too rare to warrant focus)
As a common noun (not capitalized unless at the start of a sentence), puritan or puritanical can refer to someone who is very strict -- especially about religious principles or proper behavior.