imprescriptible vs nonnegotiable

imprescriptible

adj

  • Not subject to prescription: absolute, inalienable. 

nonnegotiable

adj

  • Not negotiable; not subject to negotiation. 

noun

  • Something that is not negotiable. 

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