flagship vs prime mover

flagship

noun
  • The most important one out of a related group. 

  • The ship occupied by the fleet's commander (usually an admiral); it denotes this by flying his flag. 

  • The ship regarded as most important out of a group, e.g. a nation's navy or company's fleet. 

verb
  • To act as a flagship for. 

prime mover

noun
  • A person or thing that is seminal and influential. 

  • The front part of a semi-trailer type truck, i.e., the tractor to which the trailer part attaches. 

  • A military or heavy construction vehicle. 

  • The initial agent that is the cause of all things. 

  • A machine, such as a water wheel or steam engine, that receives and modifies energy as supplied by some natural source or fuel and transforms it into mechanical work 

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