backsword vs longsword

backsword

noun
  • A sword with one sharp edge. 

longsword

noun
  • A European sword with a long, straight double-edged blade, a cruciform hilt, and a grip for two-handed use; prevalent from the 14th to 16th centuries. 

  • Any type of sword that is comparatively long; depending on context, applied to swords of the Bronze Age, Migration period, Viking Age and Renaissance era. 

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