rover vs straggler

rover

noun
  • One who roves, a wanderer, a nomad. 

  • A position that is one of three of a team's followers, who follow the ball around the ground. Formerly a position for short players, rovers in professional leagues are frequently over 183 cm (6'). 

  • A pirate. 

  • A randomly selected target. 

  • A vagabond, a tramp, an unsteady, restless person, one who by habit doesn't settle down or marry. 

  • A remotely-operated vehicle; ROV 

  • A defensive back position whose coverage responsibilities are a hybrid of those of a cornerback, safety and linebacker. 

  • A ball which has passed through all the hoops and would go out if it hit the stake but is continued in play; also, the player of such a ball. 

  • The tenth defensive player in slow-pitch softball. 

  • A pirate ship. 

  • A vehicle for exploring extraterrestrial bodies. 

straggler

noun
  • One who roams without any settled direction. 

  • Something that stands alone or by itself. 

  • One who falls behind the rest, for example in a race. 

  • Something that shoots, or spreads out, beyond the rest, or too far; an exuberant growth. 

  • A roving vagabond. 

  • A person who straggles, or departs from the direct or proper course, or from the company to which they belong. 

  • A migratory animal found away from its usual range. 

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