sibilant vs squawky

sibilant

adj
  • Characterized by a hissing or hushing sound such as the s or sh in sack or shack. 

noun
  • A consonant having a hissing or hushing sound such as the s or sh in sack or shack. 

squawky

adj
  • Making squawking sounds. 

  • Resembling a squawk; raw and grating 

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