treaty

The noun is derived from Middle English trete, trety (“bargaining, negotiation; discussion; conference, meeting; entreaty, persuasion; agreement, contract, covenant; arrangement, settlement; agreement between two rulers, states, etc.; written work on a particular subject, treatise; subdivision of a written work, section”) [and other forms], from Anglo-Norman treté, traité, treaté, and Old French traité, traitié [and other forms] (modern French traité (“agreement between two rulers, states, etc.; treatise”)); traité or traitié is:

a noun use of the past participle of traiter (“to treat; to deal with, handle”), from Latin tractāre, the present active infinitive of tractō (“to drag, haul, tug; to handle, manage; to debate, discuss; to exercise, practise; to perform, transact”), from trahō (“to drag, pull”) + -tō (frequentative suffix); and

also from Latin tractātum (“written work on a particular subject, treatise”), from Latin tractātus (“dragged, hauled, tugged; handled, managed; exercised, practised; performed, transacted”), the perfect passive participle of tractō (see above).

The verb is derived from the noun.