hard porn vs smut

hard porn

smut

verb
  • To stain (or be stained) with soot or other dirt. 

  • To clear of the smut fungus. 

  • To taint (grain, etc.) with the smut fungus. 

  • To become tainted by the smut fungus. 

noun
  • Bad, soft coal containing earthy matter, found in the immediate locality of faults. 

  • Obscene language; ribaldry; obscenity. 

  • A flake of ash or soot. 

  • Soot. 

  • Sexually vulgar material; something that is sexual in a dirty way; pornographic material. 

  • Any of a range of fungi, mostly Ustilaginomycetes, that cause plant disease in grasses, including cereal crops; the disease so caused. 

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