third string vs underling

third string

noun
  • A unit of players that plays behind the first and second strings; a junior varsity team. 

adj
  • Of a decidedly lower quality or condition. 

underling

noun
  • A low, wretched person. 

  • A subordinate, or person of lesser rank or authority. 

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