impendent vs lowering

impendent

adj

  • impending; threatening 

lowering

adj

  • Dark and menacing. 

  • Lurking, skulking, menacing. 

  • That lowers or frowns. 

noun

  • The act of something being lowered. 

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