yo vs yourself

yo

pron
  • third-person singular, familiar 

intj
  • An expression of surprise or excitement. 

  • An interjection similar to hey. 

  • A greeting similar to hi. 

  • Present! Here! 

  • Emphatic conclusion to a statement. 

noun
  • The letter Ё, ё. 

yourself

pron
  • You (singular); used emphatically, especially to indicate exclusiveness of the referent's participation in the predicate, i.e., that no one else is involved. 

  • Your own self (singular). 

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