Ego is the Latin word for I.
"Ego sum rex Romanus" means “I am the king of Rome.”
I am hungry. I am 55 years old. I am born here. This is an uncomplicated way of using the word I.
I am a stupid old fool. I am too fat. I have a big ugly nose. This is not a very smart but still a comprehensible way of using the I-word.
He has a big ego. My ego reacted. This way of using the word ego is weird I think, though it is common in every day language. It sounds like the word I denote something, a part of a person, like an organ, like a kidney or an eye or a big nose or something.
He is very egoistic. I got very upset and angry when she called me a stupid old fool. I had a wonderful thought today. I have crazy thoughts popping in to my head. This way of using the word ego or I makes more sense to me.
I have an ego. I have an I. When did this strange way of talking begin? Did it begin with Freud?