The word diplomacy was first written down by former Irish MP Edmund Burke in 1796. He continued using it for a few years until other authors started picking it up, with usage peaking during World War I. This was borrowed from the French word diplomatie, which is from Modern Latin diplomaticus, meaning "diplomat". Here it gets interesting: that traces to the Latin word diploma, which described the official diplomatic papers that those diplomats received. This had a broader definition of "document conferring a privilege" and is also the etymon of our current English word diploma, which was adopted in the seventeenth century. The Latin term further goes back to Ancient Greek diploma, which meant "license" but more literally could be interpreted as "folded paper" because the root of it all is diplo-, "twofold" (-oma just denoted action). So both diplomacy and diplomas have creases in common.
Adam Aleksic, an incoming freshman at Harvard University, has been described as the internet's sixth most famous etymologist. He has disturbing interests in linguistics, vexillology, geography, board games, limericks, and law, and he loves writing about himself in the third person.
The Etymology Nerd