louring vs lowering

louring

noun

  • The act of one who, or that which, lours. 

lowering

noun

  • The act of something being lowered. 

adj

  • Dark and menacing. 

  • Lurking, skulking, menacing. 

  • That lowers or frowns. 

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