inconsonant vs sibilant

inconsonant

adj

  • Not consonant; disagreeing or clashing 

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. 

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