piece of doggerel vs poem

piece of doggerel

poem

noun
  • A piece of writing in the tradition of poetry, an instance of poetry. 

  • A piece of poetic writing, that is with an intensity or depth of expression or inspiration greater than is usual in prose. 

  • A literary piece written in verse. 

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