galley slave vs navvy

galley slave

noun

  • A slave who rows in a galley (type of ship). 

navvy

noun

  • A laborer on a civil engineering project such as a canal or railroad. 

verb

  • To carry out physical labor on a civil engineering project. 

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