collard greens vs collet

collard greens

noun
  • A form of Brassica oleracea, sometimes called Brassica oleracea var. acephala or Brassica oleracea var. viridis, similar to kale, that is a popular food in the rural southern United States. 

collet

noun
  • A band, flange, ferrule, or collar, designed to grip and hold a tool or a workpiece under proper control, and usually to release it under control thereafter; such a collet usually is made of a hard, springy material, especially a metal. 

  • The rim (of a ring) within which a jewel is set. 

  • In an embryonic plant, the transition zone between the root and the hypocotyl (not clearly distinguishable in most plants.) 

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