before vs on top of that

before

prep
  • In the presence of. 

  • In front of, according to a formal system of ordering items. 

  • In store for, in the future of (someone). 

  • At a higher or greater position than, in a ranking. 

  • Under consideration, judgment, authority of (someone). 

  • In front of in space. 

  • Earlier than (in time). 

conj
  • Rather or sooner than. 

  • In advance of the time when. 

adv
  • At an earlier time. 

  • In advance. 

  • At the front end. 

on top of that

prep
  • Also, additionally, moreover. 

How often have the words before and on top of that occurred in a corpus of books? (source: Google Ngram Viewer )