fricative vs sibilous

fricative

adj
  • produced by air flowing through a restriction in the oral cavity. 

noun
  • Any of several sounds produced by air flowing through a constriction in the oral cavity and typically producing a sibilant, hissing, or buzzing quality; a fricative consonant. 

sibilous

adj
  • Having a hissing sound; sibilant. 

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