English

letter agreement

letter + agreement

Latin littera ‘letter of the alphabet; (plural) epistle’

Old French letre

Middle English letter

Old French agrement ‘agreement’

Middle English agrement ‘an understanding, agreement’

Today it means

noun An agreement, specifically a legally binding contract, reached by the parties' exchange of letters.

Language periods are conventional ranges, not dates for this word.

Etymograph / letter agreement