The Greek reflexive pronoun hautou (αὑτοῦ) means "of himself," "of itself," or "of their own accord" — it intensifies the reflexive nature of an action done by or to the subject itself. It is a contracted form of heautou and appears in contexts emphasizing self-reference or self-determination.
The reflexive pronoun hautou appears at a critical moment in John 18:17: Peter denies Christ — "I am not one of his disciples" — using language of self-distancing. The reflexive force is ironic: in denying Christ, Peter was denying himself, his own calling. The deepest theological use of this concept is Philippians 2:7: Christ "emptied himself (heauton ekenosen)" — the voluntary self-emptying of the Son of God. Divine humility is the supreme use of reflexive action.