irritant vs source of vexation

irritant

adj

  • Causing irritation or inflammation. 

  • Rendering null and void; conditionally invalidating. 

noun

  • Any medication designed to cause irritation 

  • A source of irritation. 

source of vexation

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