perspire vs swelter

perspire

verb
  • To emit (sweat or perspiration) through the skin's pores. 

  • To be evacuated or excreted, or to exude, through the pores of the skin. 

swelter

verb
  • To perspire greatly from heat. 

  • To cause to faint, to overpower, as with heat. 

  • To suffer terribly from intense heat. 

noun
  • Intense heat. 

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