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