expand vs grow fatter

expand

verb
  • To become, by rewriting, a longer, yet equivalent sum of terms. 

  • To feel generous or optimistic. 

  • To multiply both the numerator and the denominator of a fraction by the same natural number yielding a fraction of equal value 

  • To change (something) from a smaller form or size to a larger one; to spread out or lay open. 

  • To change or grow from smaller to larger in form, number, or size. 

  • To rewrite (an expression) as a longer, yet equivalent sum of terms. 

  • To increase the extent, number, volume or scope of (something). 

  • To express (something) at length and/or in detail. 

  • To increase in extent, number, volume or scope. 

  • To speak or write at length or in detail. 

grow fatter

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