hallucinogenic vs unimaginable

hallucinogenic

adj

  • producing hallucinations 

noun

  • a substance that is a hallucinogen. 

unimaginable

adj

  • unable to be imagined; inconceivable or mind-boggling; beyond belief 

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