constable vs sergeant

constable

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

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

  • The warden of a castle. 

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

  • A police officer or an officer with equivalent powers. 

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

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

sergeant

noun
  • The highest rank of noncommissioned officer in some non-naval military forces and police. 

  • A fish, the cobia. 

  • A title sometimes given to the servants of the sovereign. 

  • A bailiff. 

  • UK army rank with NATO code OR-6, senior to corporal and junior to warrant officer ranks. 

  • Any of various nymphalid butterflies of the genus Athyma; distinguished from the false sergeants. 

  • A lawyer of the highest rank, equivalent to the doctor of civil law. 

  • A servant in monastic offices. 

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