second string vs underling

second string

noun
  • A unit of players which is considered to have a secondary level of talent and which usually plays after the first string. 

adj
  • Not as good; of a lower quality or condition. 

underling

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

  • A low, wretched person. 

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