As is the case with most dishes—nobody knows for sure. The most likely origin of moussaka seems to be Arabia or the Levant. An Ottoman, Turabi Efendi, later published the first written recipe of moussaka in his "Turkish Cookery Book" in 1862. However, most people associate moussaka with Greece. That's because in 1920s, a French-educated Greek chef, Nikos Tselementes, modernized the recipe by adding the classic French mother sauce: béchamel. Tensions were high between Turks and Greeks at that time, so it is likely that Chef Tselementes wanted to "Europeanize" the dish as much as possible. In short: moussaka most likely originated in the Levant and made its way to Turkey, where it was adopted and modernized by Greeks by way of adding French béchamel sauce to the dish.