constable vs sapper

constable

noun
  • A police officer or an officer with equivalent powers. 

  • An elected or appointed public officer, usually at municipal level, responsible for maintaining order or serving writs and court orders. 

  • One holding the lowest rank in most Commonwealth police forces. (See also chief constable.) 

  • The warden of a castle. 

  • An officer of a noble court in the Middle Ages, usually a senior army commander. (See also marshal). 

  • An elected head of a parish (also known as a connétable) 

  • A large butterfly, Dichorragia nesimachus, family Nymphalidae, of Asia. 

sapper

noun
  • An officer or private of the Royal Engineers. 

  • Historical term for a combat engineer that is still used in some armies, in other words an engineer or a soldier engaged in attacking, destroying, and circumventing or building fortifications, bridges, and roads; a military engineer active in a combat zone. 

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