Where does “in agreement” come from?

in agreement (English) comes from English agreement, from Middle English agrement, from Old French agrement, from Old French agreer, from Old French gré, from Latin grātum, from Latin grātus, from Proto-Italic grātos — to express approval; praise; to elevate.

Ancestry of “in agreement”, step by step

in agreement traces back through two separate lines of ancestry.

via English agreement

StepLanguageWordMeaning
1EnglishagreementAn understanding between entities to follow a...
2Middle EnglishagrementAn understanding, agreement, or state of mutual...
3Old Frenchagrementagreement; accord
4Old Frenchagreerto please; to be pleasing to
5Old Frenchgrépleasure, goodwill; will; step
6Latingrātum
7Latingrātuspleasing, acceptable, agreeable, welcome
8Proto-Italicgrātos
9Proto-Indo-Europeangʷr̥Htóspraised
10Proto-Indo-EuropeangʷerH-to express approval; praise; to elevate

via English in

StepLanguageWordMeaning
1EnglishinUsed to indicate location, inclusion, or position...
2Middle EnglishinAny kind of accomodation; particularly; A home or...
3Old Englishinin; Alternative form of inn
4Proto-West Germanic*in
Every word from Proto-Indo-European gʷerH-Every word from Proto-Indo-European gʷr̥HtósEvery word from Proto-Italic grātos
in agreement — Etymology, Origin & Word History | Etymology Explorer