Ego is defined as "I", both being of Latin derivation. Ego is a very misunderstood term, for it literally means "the self." The psychologist Sigmund Freud saw the ego as something of an intelligent administrator concerned with keeping the person going in the face of adversity.
The ego is not personality per se, although it is a part which remains with the soul even after death. The ego represents a false minded perception of the self as you desire to be, rather than the real you. Ego represents a part of the individuated expression of the soul, and more easily expressed through personality. The physical personality on the other hand, while imprinted at birth, developed or molded during life, diminishes with death.
The ego is not the most knowledgeable or powerful portion of the self. It appears to dominate during physical life, but is subdued after death where the non-physical personality realigns its psychological components.
We seek to shed our ego, through successive lifetimes, for it is ego that binds us to the physical world. Time will cease when we all overcome ego. This is because ego consciousness identifies with biological matter and earthly experiences, whereas the higher self is closer to the source--which is pure love and light.