labor vs moonlight

labor

moonlight

verb
  • To engage in an activity other than what one is known for. 

  • To work on the side (at a secondary job), often in the evening or during the night. 

  • To perform a secondary function substantially different from its supposed primary function, as in protein moonlighting. 

noun
  • The light reflected from the Moon. 

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