read up vs rub up

read up

verb
  • To learn (about something) by reading. 

rub up

verb
  • To create (something) by rubbing. 

  • To polish or scrub; to cover (something with a substance) by rubbing. 

  • To rub (a body part): to massage, give a massage to. 

  • To assault (someone). 

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