dairy cow vs milch cow

dairy cow

noun
  • A cow bred for the ability to produce large quantities of milk, from which dairy products are made. 

  • A black-and-white varietal of the Porcellio laevis woodlouse. 

milch cow

noun
  • A cow that produces milk (having had at least one calf). 

  • A cash cow. 

  • A cow kept for milking; a dairy cow. 

  • A German WWII submarine designed to carry large cargoes of supplies and transfer them to other submarines. 

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