There are countless Sci-Fi works featuring Energy Swords. But, which one was the first? Which one bring this idea in the world?
Strict definition of an Energy Sword can be complex because of variations of swords (Plasma blade, Concentrated Photon blade, Low heat blade etc). Just take reference of Lightsabers (Star Wars). Some features I am highlighting however:
The blade isn't made of any kind of solid matter (fictional or real).
The blade is projected as light beam which can be turned off.