lewd vs rock hard

lewd

verb
  • To express lust; to behave in a lewd manner. 

noun
  • A sexually suggestive image, particularly one which does not involve full nudity. 

adj
  • Lascivious, sexually promiscuous, rude. 

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 

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