insignificant vs irrelevant

insignificant

adj
  • Not significant; not important, inconsequential, or having no noticeable effect. 

  • Without meaning; not signifying anything. 

irrelevant

adj
  • Not usefully related: not associated in any way that is important or useful to the context being discussed: not materially applicable; having connections not applicable in the present situation. 

  • Not at all related: totally unrelated, wholly unconnected, completely inapplicable. 

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