pachydermatous vs unsusceptible

pachydermatous

adj

  • Of or relating to the pachyderms. 

  • Like an elephant 

  • Thick-skinned; insensitive. 

unsusceptible

adj

  • Not susceptible. 

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