refill vs top something up

refill

verb
  • To repeat a prescription. 

  • To fill up once again. 

noun
  • A repeat of a prescription. 

  • An additional helping of food or drink. 

  • A filling after the first. 

  • A product containing materials to replace those used up by a piece of equipment. 

top something up

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