taboo vs undocumented

taboo

adj
  • Culturally forbidden. 

  • Excluded or forbidden from use, approach or mention. 

noun
  • An inhibition or ban that results from social custom or emotional aversion. 

  • Something which may not be used, approached or mentioned because it is sacred. 

verb
  • To ban. 

  • To avoid. 

  • To mark as taboo. 

undocumented

adj
  • Not having official documentation required to legally enter, reside in, or work in a country. 

  • Lacking instructions or reference material. 

  • Not having official documents that provide identification, authorization, etc. 

noun
  • Synonym of undocumented immigrant 

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