hum vs tough

hum

intj
  • Synonym of um: a noise indicating doubt, uncertainty, &c. 

  • Synonym of hmm: a noise indicating thought, consideration, &c. 

verb
  • To produce low sounds which blend continuously 

  • To express by humming. 

  • To reek, smell bad. 

  • To make a sound from the vocal chords without pronouncing any real words, with one's lips closed. 

  • To drone like certain insects naturally do in motion, or sounding similarly 

  • To buzz, be busily active like a beehive 

noun
  • Unpleasant odour. 

  • A phenomenon, or collection of phenomena, involving widespread reports of a persistent and invasive low-frequency humming, rumbling, or droning noise not audible to all people. 

  • Busy activity, like the buzz of a beehive. 

  • A hummed tune, i.e. created orally with lips closed. 

  • An often indistinct sound resembling human humming. 

tough

intj
  • Used to indicate lack of sympathy 

verb
  • To endure. 

  • To toughen. 

adj
  • Harsh or severe. 

  • Difficult or demanding. 

  • Stubborn or persistent; capable of stubbornness or persistence. 

  • Strong and resilient; sturdy. 

  • Undergoing plastic deformation before breaking. 

  • Difficult to cut or chew. 

  • Rugged or physically hardy. 

  • Rowdy or rough. 

noun
  • A person who obtains things by force; a thug or bully. 

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