briefs vs trousers

briefs

noun
  • A very short, close-fitting type of underpants. 

trousers

noun
  • An article of clothing that covers the part of the body between the waist and the ankles or knees, and is divided into a separate part for each leg. 

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