Stories We Like: A Guide to the Comma
1796, from French diplomatie, formed from diplomate "diplomat" (on model of aristocratie from aristocrate), from Latin adjective diplomaticos, from diploma (genitive diplomatis) "official document conferring a privilege" (see diploma; for sense evolution, see diplomatic).
It is obvious to any one who has been in charge of the interests of his country abroad that the day secrecy is abolished negotiations of any kind will become impossible. [Jules Cambon, "The Diplomatist" (transl. Christopher Rede Turner), 1931]