asyndeton vs echoism

asyndeton

noun
  • A stylistic scheme in which conjunctions such as "or" and "and" are deliberately omitted from a series of words, phrases, or clauses. 

echoism

noun
  • The practice of creating words or language by imitating sounds from the environment. 

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