ego (n.)

1714, as a term in metaphysics, "the self; that which feels, acts, or thinks," from Latin ego "I" (cognate with Old English ic; see I). Psychoanalytic (Freudian) sense is from 1894; sense of "conceit" is 1891. Ego-trip first recorded 1969, from trip (n.). Related: egoical; egoity.
In the book of Egoism it is written, Possession without obligation to the object possessed approaches felicity. [George Meredith, "The Egoist," 1879]