field artillery vs long Tom

field artillery

noun
  • The part of an army's artillery which consists of (light) fieldpieces (cannons, howitzers) which are mobile enough to deploy on the (battle) field, as opposed to the fixed guns in fortifications or naval artillery; usually excludes antiaircraft. 

long Tom

noun
  • Any of various early cannon and field guns. 

  • A high-powered lens for long-distance filming or photography. 

How often have the words field artillery and long Tom occurred in a corpus of books? (source: Google Ngram Viewer )