informal vs undocumented

informal

adj
  • Not organized; not structured or planned. 

  • Reflecting everyday, non-ceremonious usage. 

  • Suited for everyday use. 

  • Not in accord with the usual regulations. 

  • Not formal or ceremonious. 

undocumented

adj
  • Lacking instructions or reference material. 

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

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

noun
  • Synonym of undocumented immigrant 

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