diploma

Diploma in Greek means a letter folded double, a document, from diploun (to fold double), from diploos (double, twofold), from di- (two) + -ploos (fold). In Roman usage, a diploma was an official document — a passport, a certificate, a letter of recommendation. Soldiers received a diploma at discharge listing their rights and privileges. The document was folded and sealed. The folding was the security feature.

The word 'diplomat' did not exist until the late eighteenth century. Before that, ambassadors, envoys, and legates conducted international relations. Edmund Burke used 'diplomatic' in 1796. The French word diplomate appeared around the same time. The coinage reflected a shift: international relations were becoming professionalized, institutionalized, and — above all — documented. The diplomat was the person who handled the documents.

The Congress of Vienna (1814-1815) established the modern diplomatic system. Diplomatic immunity, diplomatic protocol, diplomatic ranks (ambassador, minister, charge d'affaires) were formalized. The word 'diplomacy' — the art and practice of conducting international relations — became standard. Talleyrand, Metternich, and Castlereagh were the first generation of self-conscious diplomats in the modern sense.

In everyday English, 'diplomatic' has come to mean tactful, careful with words, avoiding offense. 'She was very diplomatic about the mistake.' This usage preserves the diplomat's most important skill — saying difficult things without provoking a war. The folded document became a professional class became a personality trait.