unmentioned vs voiceless

unmentioned

adj
  • Not mentioned. 

voiceless

adj
  • Lacking a voice, without vocal sound. 

  • Spoken without vibration of the vocal cords; unvoiced, surd, breathed. Examples: [t], [s], [f], [m̥], [u̥]. 

  • Without a vote; having no input into a decision. 

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