frock vs swallowtail

frock

noun
  • An undress regimental coat. 

  • An outer garment worn by priests and other clericals; a habit. 

  • A sailor's jersey. 

  • A frog. 

  • A dress, a piece of clothing, which consists of a skirt and a cover for the upper body. 

verb
  • To make (somebody) a cleric. 

  • To clothe (somebody) in a frock. 

  • To grant to an officer the title and uniform of a rank he will soon be promoted to. 

swallowtail

noun
  • A type of tailcoat with two long tapering tails.ᵂᵖ 

  • The forked tail of a swallow. 

  • Anything, such as a burgee, of a similar forked shape. 

  • Any of various butterflies of the family Papilionidae, many of which have a long extension to each hindwing. 

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