abirritate vs slack off

abirritate

verb
  • To diminish the sensibility of; to debilitate; to soothe. 

slack off

verb
  • To decrease in intensity; to ease off; to diminish; to die down. 

  • To be deliberately unproductive in one's work or study. 

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