dissimilar vs indistinguishable

dissimilar

adj

  • Not similar; unalike; different 

indistinguishable

adj

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

  • Not capable of being perceived or known. 

noun

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

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