The phrases persona grata and persona non grataare widely used in English and other modern European languages, but their origin and development have never been fully investigated. They do not belong to classical or patristic Latin: rather, persona grata originates in the language of late medieval ecclesiastical diplomacy. After sporadic use from the 15th century to the end of the 18th, it and similar forms of words became very important in negotiations between the Protestant monarchies of Germany and the Holy See in and around the 1820s. Persona grata was then transferred to the language of international diplomacy, where it has flourished since the 1850s; the negative persona non grata, which is now more common than the positive phrase, appears to have developed in English-language contexts in the nineteenth century.