penning vs poem

penning

noun
  • Writing; literary composition. 

  • An old currency unit, the Swedish penning. 

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 penning and poem occurred in a corpus of books? (source: Google Ngram Viewer )