burgee vs labarum

burgee

noun
  • A flag, usually a broad tapering pennant, often with a swallowtail, flown by yachts to identify the owner's yacht club. 

labarum

noun
  • The Roman military standard adopted by Constantine I. The banner was known for its Christian chi-rho sign - ☧. 

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