Etymology
Advertisement
ego (n.)

by 1707, in metaphysics, "the self; that which feels, acts, or thinks," from Latin ego "I" (cognate with Old English ic; see I); its use is implied in egoity.

They that have pleaded against Propriety, and would have all things common in this World, have forgotten that there is a Propriety, in our present Egoity, and Natural Constitution, which rendereth some accidental Propriety necessary to us (etc.) ["The Practical Works of the Late Reverend and Pious Mr. Richard Baxter," London, 1707]

Psychoanalytic (Freudian) sense is from 1894; sense of "conceit" is 1891. Ego-trip first recorded 1969, from trip (n.). Related: egoical.

In the book of Egoism it is written, Possession without obligation to the object possessed approaches felicity. [George Meredith, "The Egoist," 1879]
Related entries & more 
Advertisement
super-ego (n.)
also superego, "that part of the psyche which controls the impulses of the id," 1924, as a translation of German über-Ich; see super- and ego.
Related entries & more 
egocentric (adj.)
1890, from ego + -centric. Related: Egocentricity; egocentrism.
Related entries & more 
egotize (v.)
"talk overmuch of oneself," 1775, from ego + -ize.
Related entries & more 
egotheism (n.)
"deification of the self," 1855, from ego + -theism. Related: Egotheist (1849); egotheistic.
Related entries & more 
Advertisement
egotist (n.)
1714, "one who makes too frequent use of the first-person singular pronoun," see ego + -ist. First attested in Joseph Addison (see egotism). Related: Egotistic; egotistical; egotistically.
Related entries & more 
egoist (n.)
1763, in metaphysics, "one who maintains there is no evidence of the existence of anything but the self" (taking ego in a sense of "thinking subject"), from French égoiste (1755); see ego + -ist. Meaning "selfish person" is from 1879. Related: Egoistic; egoistical.
Related entries & more 
egotism (n.)
1714, "too frequent use of 'I'," from ego + -ism. First used by Joseph Addison, who credits the term to "Port-Royalists" who used it in reference to obtrusive use of first person singular pronoun in writing, hence "talking too much about oneself." Meaning "self-conceit, selfishness" is from 1800. The -t- is abnormal, perhaps by influence of dogmatism.
Related entries & more 
egoism (n.)
1785, in metaphysics, "the theory that a person has no proof that anything exists outside his own mind," from French égoisme (1755), from Modern Latin egoismus, from Latin ego (see ego). Meaning "doing or seeking of that which affords pleasure or advances interest" is from 1800; opposed to altruism, but not necessarily "selfish." Meaning "self-centeredness" is from 1840. Between egoism and egotism, egoism is more correctly formed; there formerly was a useful distinction, with egotism tending to take the senses "self-centeredness" and "extensive use of 'I'" and leaving to egoism the theoretical sense in metaphysics and ethics.
Related entries & more 
egomania (n.)

"obsessive self-centeredness," 1825 (in a letter of English critic William Sidney Walker, published in 1852), from ego + mania. Not in common use before 1890s, where it translated German Ich-Sucht.

[The egomaniac, as opposed to the megalomaniac,] does not regard it as necessary to dream of himself as occupying some invented social position. He does not require the world or its appreciation to justify in his own eyes himself as the sole object of his own interest. He does not see the world at all. Other people simply do not exist for him. The whole 'non-Ego' appears in his consciousness merely as a vague shadow or a thin cloud. The idea does not even occur to him that he is something out of the common, that he is superior to other people, and for this reason either admired or hated ; he is alone in the world ; more than that, he alone is the world and everything else, men, animals, things are unimportant accessories, not worth thinking about. [Max Nordau, "Degeneration," English translation, 1895]

Nordau's book was much-read, debated, and cited at the time and the word was associated with him (e.g. The Agora, July 1895).

Walker's use aside, its infrequent print appearance before 1895 seems to have been largely in the side of medicine that dealt with psychological matters:

The most frequent, yet the most extraordinary of these perversions of temper, are seen in young females. It is a species of aberration of the intellect, but short of insanity, real enough, but exaggerated, fictitious, factitious, and real at the same time. It frequently has its origin in dyspepsia, hysteria, or other malady, and in emotion of various kinds, such as disappointment, vexation, &c. Its object is frequently to excite and to maintain a state of active sympathy and attention, for which there, is as it were, a perpetual, morbid, and jealous thirst. It was rather aptly designated, by the clever relative of one patient, an ego-mania. [Marshall Hall, M.D., "Practical Observations and Suggestions in Medicine," London, 1845]
Related entries & more