frequentative vs periodical

frequentative

adj
  • Serving to express repetition of an action. 

noun
  • Any of a subclass of imperfective verbs that denote a repeated action, no longer productive in English, but found in e.g. Finnish, Latin, Russian, and Turkish. 

periodical

adj
  • Periodic. 

  • Published at regular intervals of more than one day, especially weekly, monthly, or quarterly. 

  • Of, or relating to such a publication. 

noun
  • A regularly issued thematic publication that contains the most current information in its field, often the primary means for communication of original scholarship or creative work at the cutting edge of research in its field. 

  • A publication issued regularly, but less frequently than daily. 

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