extenuation vs palliation

extenuation

noun
  • The action of lessening, or seeking to lessen, the guilt of (an offence or fault) by alleging partial excuses; and instance or means of doing this; a plea in mitigation of censure. 

  • The action of representing (something) as slight and trifling; underrating; an instance of this, a plea to this end; a modification in terms. 

  • The action or process of making or becoming thin; an instance of this; a shrunken condition; leanness, emaciation. 

  • Thin garments. 

palliation

noun
  • Extenuation; mitigation. 

  • The alleviation of a disease's symptoms without a cure; temporary relief. 

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