pais
/peɪ/ /peɪz/Law
noun
in pais: in or within the country; relating to or designating actions, matters, etc., which are legally recognized despite not being formally recorded or performed. Also (and now frequently) in estoppel in pais: estoppel in respect of things expressed or implied by one party, which may not subsequently be disavowed to the detriment of the other party.
Origin
Early 17th century; earliest use found in Edward Coke (1552–1634), lawyer, legal writer, and politician. From Law French pais (Anglo-Norman pais), specifically use of Anglo-Norman and Old French, Middle French pais country from post-classical Latin pagensis of or relating to the country or a country district.