rock hard vs rockhard

rock hard

adj
  • With strongly held beliefs and opinions, deep conviction. 

  • As tough, hard, or inflexible as a piece of rock. 

  • With muscles developed and toned to a high degree, especially the muscles of the abdomen. 

  • Having a very fully erect and stiff penis 

rockhard

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