lettering vs periodical

lettering

noun
  • Written text, especially when printed. 

periodical

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

  • 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. 

adj
  • Periodic. 

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

  • Of, or relating to such a publication. 

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