1714 the physical self (metaphysics explains physical world from outside of physical world)
1800 excessive appreciation of oneself (egotism)
1894 the self as opposed to the subconcious, the ego is diseased by subconcious desires (psycho-analytics/Freud)
1969 ego trip - a course of action that enhances and satisfies the ego
I suspect having a "big ego" means seeing yourself as more than just a person, including the objects you own, your land, and people you influence, and controlling those things for your own beneifit. The president might get a big ego, thinking himself as more than simply a man holding an office that has to work hard to live up to expectations. A big ego might be more like a delusion of grandeur, when you really aren't that powerful/smart, you have just been handed some power/information/wealth.
You probably make people feel inferior, or think you have abilities and fail to see other people's abilities or appreciate what they've accomplished. That sort of thing.
"Losing your ego" is going to mean you aren't concerned with what happens, and you are going to let other people decide what goes on. When you think about how coincidental it is that you are where you happen to be, and see yourself as a part of a whole, and empathize with others even when they are disagreeable. Giving up your power in order to stay humble, accepting your lot in life.
What do people hope to accomplish by telling you to rid yourself of an ego? They see you as part of the collective that you are part of and need to get you to see it. Once you are free of egos, nobody will suffer or undermine one another to get ahead. Which actually sounds more like losing your id, rather than your ego. I doubt most people are truly involved in such a noble pursuit.
That is what I figure. I came here asking the same question. A person without ego is willing to give up everything.
It seems like a word people use for a variety of different meanings that are diffiicult to determine, they may use it without being able to explain what they mean.