oneself vs themselves

oneself

pron
  • A person's self: general form of himself, herself, themself or yourself. 

themselves

pron
  • The reflexive case of they, the third-person singular personal pronoun. The single person previously mentioned, as the object of a verb or following a preposition (also used for emphasis). 

  • The reflexive case of they, the third-person plural personal pronoun. The group of people, animals, or objects previously mentioned, as the object of a verb or following a preposition (also used for emphasis). 

How often have the words oneself and themselves occurred in a corpus of books? (source: Google Ngram Viewer )