Unity

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Middle English: from Old French unite, from Latin unitas, from unus ‘one’.

wiktionary

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From Anglo-Norman unité, Old French unité, from Latin ūnitās, from ūnus(“one”) + noun of state suffix -itās.

etymonline

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unity (n.)

c. 1300, "state or property of being one," from Anglo-French unite, Old French unite "uniqueness, oneness" (c. 1200), from Latin unitatem (nominative unitas) "oneness, sameness, agreement," from unus "one" (from PIE root *oi-no- "one, unique").