backboneless vs milky

backboneless

adj
  • Cowardly, spineless. 

  • Without a backbone; invertebrate. 

milky

adj
  • Cowardly. 

  • Containing a whitish liquid, juicy. 

  • Containing (an especially large amount of) milk. 

  • Of the black in an image, appearing as dark gray rather than black. 

  • Resembling milk in color, consistency, smell, etc.; consisting of milk. 

  • Immature, childish. 

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