whatshisface vs whosit

whatshisface

noun
  • A person whose name is either unknown or forgotten 

whosit

noun
  • A specific person (used in a vague way to refer to someone whose name one cannot recall) 

  • A thing (used in a vague way to refer to something whose name one cannot recall or is embarrassed to say) 

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