adieu vs adios

adieu

noun
  • A farewell, a goodbye; especially a fond farewell, or a lasting or permanent farewell. 

intj
  • Said to wish a final farewell; goodbye. 

adios

noun
  • A goodbye. 

intj
  • goodbye 

verb
  • To get rid of. 

  • To leave; to literally or figuratively say “adios” to. 

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