What is the X in X-mas?
Old English self, seolf, sylf "one's own person, -self; own, same," from Proto-Germanic *selbaz (cf. Old Norse sjalfr, Old Frisian self, Dutch zelf, Old High German selb, German selb, selbst, Gothic silba), Proto-Germanic *selbaz "self," from PIE *sel-bho-, suffixed form of root *s(w)e-, pronoun of the third person and reflexive (referring back to the subject of a sentence), also used in forms denoting the speaker's social group, "(we our-)selves" (see idiom).
Trying to define yourself is like trying to bite your own teeth. [Alan Watts]Its use in compounds to form reflective pronouns grew out of independent use in Old English. As a noun from early 14c.
n. pl. selves (sělz)
The total, essential, or particular being of a person; the individual.
One's consciousness of one's own being or identity; the ego.
the "I" as experienced by an individual. In modern psychology the notion of the self has replaced earlier conceptions of the soul