metonymic vs metonymical

metonymic

adj
  • Of, or relating to, a word or phrase that names an object from a single characteristic of it or of a closely related object. 

noun
  • Synonym of metonym, an instance of metonymy. 

metonymical

adj
  • Synonym of metonymic, of or relating to metonymy. 

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