glower vs knit/furrow one's brows

glower

noun

  • An angry glare or stare. 

  • That which glows or emits light. 

verb

  • To look or stare with anger. 

knit/furrow one's brows

How often have the words glower and knit/furrow one's brows occurred in a corpus of books? (source: Google Ngram Viewer )