Treaty

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late Middle English: from Old French traite, from Latin tractatus ‘treatise’ (see tractate).

wiktionary

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From Middle English trety, tretee, from Old French traitié, traieté, from Latin tractatus, from tracto.

etymonline

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treaty (n.)

late 14c., "treatment, discussion," from Anglo-French treté, Old French traitié "assembly, agreement, dealings," from Latin tractatus "discussion, handling, management," from tractare "to handle, manage" (see treat (v.)). Sense of "contract or league between nations or sovereigns" is first recorded early 15c.