shipworm vs woodworm

shipworm

noun
  • Any of several wormlike marine mollusks (not true worms) of the family Teredinidae, that bore through the wooden hulls of ships and other woody material immersed in salt water. 

woodworm

noun
  • A shipworm, a worm-like mollusk in the family Teredinidae that feeds on wood underwater in saltwater. 

  • Any of many beetle larvae that bore into wood. 

  • Anobium punctatum, the Common Furniture Beetle. 

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