Zeppelin vs zeppelin

Zeppelin

noun
  • A type of large dirigible rigid airship of the early 20th century, built by the German Luftschiffbau Zeppelin and designed to carry passengers or bombs. 

  • A rigid airship dirigible, not restricted to Germany nor the early 20th century. 

name
  • A German manufacturing company, famed for building the zeppelin airships. 

zeppelin

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