overcoat vs trench coat

overcoat

noun
  • A heavy garment worn over other clothes, for protection from cold or weather. 

verb
  • To apply an exterior coating to. 

trench coat

noun
  • A military-style raincoat with a belt and deep pockets and often epaulettes. 

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