Purity

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Middle English: from Old French purete, later assimilated to late Latin puritas, from Latin purus ‘pure’.

wiktionary

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pure +‎  -ity, from Old French purete, from Latin puritas. 

etymonline

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purity (n.)

c. 1200, purite, "freedom from moral contamination, sinlessness, innocence; righteousness; chastity," from Old French purete "simple truth," earlier purte (12c., Modern French pureté), from Late Latin puritatem (nominative puritas) "cleanness, pureness," from Latin purus "clean, pure, unmixed; chaste, undefiled" (see pure (adj.)). From mid-15c. as "freedom from admixture or adulteration."