D defs.my
Entry 1 sense Webster, 1913

Oneself

/(wŭn`sĕlf")/ · One·self · IPA /wʌnˈsɛlf/
01 pron. A reflexive form of the indefinite pronoun one. Commonly written as two words, one's self.
  1. 1.
    A reflexive form of the indefinite pronoun one. Commonly written as two words, one's self.
    “One's self (or more properly oneself), is quite a modern form. In Elizabethan English we find a man's self = one's self.” — Morris.