laser beam vs rocket salad

laser beam

noun
  • The light emitted by a laser. 

  • A low, hard-hit or -thrown ball. 

rocket salad

noun
  • rocket, arugula 

  • a salad that uses the leaves of this plant as its main ingredient 

How often have the words laser beam and rocket salad occurred in a corpus of books? (source: Google Ngram Viewer )