keeper vs sentinel

keeper

noun
  • A person charged with guarding or caring for, storing, or maintaining something; a custodian, a guard; sometimes a gamekeeper. 

  • The player charged with guarding a goal or wicket. Short form of goalkeeper, wicketkeeper. 

  • One who keeps (retains) something. 

  • A fruit or vegetable that keeps (remains good) for some time without spoiling. 

  • Synonym of armature (“piece of metal connecting the poles of a magnet to preserve its strength by forming a circuit”) 

  • One who remains or keeps in a place or position. 

  • A person or thing worth keeping. 

  • A thin, flexible tress or tongue of material (e.g. leather) at the end of a crop opposite the handle, which is broad enough to prevent the horse's skin from being marked as it might be by a whip. 

  • A part of a mechanism that catches or retains another part, for example the part of a door lock that fits in the frame and receives the bolt. 

  • An offensive play in which the quarterback runs toward the goal with the ball after it is snapped. 

sentinel

noun
  • A sentry, watch, or guard. 

  • A unique string of characters recognised by a computer program for processing in a special way; a keyword. 

  • A sentinel crab. 

  • A sign of a health risk (e.g. a disease, an adverse effect). 

verb
  • To post as guard. 

  • To post a guard for. 

  • To watch over as a guard. 

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