The nickname of Midoriya Izuku is DEKU. It’s not the word for a hero, because DEKU is associated with the Japanese word “DEKUNOBO”, which means “good for nothing”.
Why is Izuku called Deku?
The one who first called Izuku Deku is Bakugo Katsuki. He read his kanji letters differently from the right one with a mocking intention.
The name Deku is an insult to Izuku, but Uraraka Ochaco gave it a new meaning when he started his life at Yuei high school. She said “Deku sounds like “you can do it!”, so I kinda love it”.
He made it his hero name later. I think it describes his life itself. He was nothing. But he met someone who gave him a new power, and he grabbed the chance tight and became strong. The good-for-nothing DEKU was reborn and got a new meaning as a hero!
Check out this article also to learn the full meaning of the name Midoriya Izuku 😉