favor vs rust

favor

verb
  • To resemble; especially, to look like (another person). 

  • To do a favor [noun sense 1] for; to show beneficence toward. 

  • To look upon fondly; to prefer. 

  • To use more often. 

  • To encourage, conduce to 

  • To treat with care. 

noun
  • A small gift; a party favor. 

  • Mildness or mitigation of punishment; lenity. 

  • A kind or helpful deed; an instance of voluntarily assisting (someone). 

  • Partiality; bias 

  • Goodwill; benevolent regard. 

  • The object of regard; person or thing favoured. 

rust

noun
  • A similar substance based on another metal (usually with qualification, such as "copper rust"). 

  • A disease of plants caused by a reddish-brown fungus. 

  • Damage caused to stamps and album pages by a fungal infection. 

  • The deteriorated state of iron or steel as a result of moisture and oxidation. 

  • A reddish-brown color. 

verb
  • To (cause to) degenerate in idleness; to make or become dull or impaired by inaction. 

  • To oxidize, especially of iron or steel. 

  • To cause to oxidize. 

  • To be affected with the parasitic fungus called rust. 

  • Of a black cat or its fur, to turn rust-coloured following long periods of exposure to sunlight. 

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