ranker vs troopship

ranker

noun
  • A common soldier. 

  • One who ranks things, or arranges them in ranks. 

  • A kind of soil developed over non-calcareous material, usually rock. 

  • One with a specified rank. 

troopship

noun
  • A ship used to transport military troops. 

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