dip pen vs gladius

dip pen

noun
  • A kind of pen consisting of a nib with capillary channels like those of a fountain pen, mounted in a handle or holder. 

gladius

noun
  • A pen, a hard internal bodypart of certain cephalopods, made of chitin-like material. 

  • A Roman sword roughly two feet long. 

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