incommensurable vs indistinguishable

incommensurable

adj
  • Not able to be measured by the same standards as another term in the context. 

  • having a ratio that is not expressible as a fraction of two integers. 

  • having no common integer divisor except 1. 

noun
  • An incommensurable value or quantity; an irrational number. 

indistinguishable

adj
  • Not capable of being perceived or known. 

  • Not distinguishable; not capable of being perceived, known, or discriminated as separate and distinct 

noun
  • Any of a set of things that cannot be distinguished. 

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