apart vs on top of that

apart

prep
  • Apart from. 

adv
  • Aside; away; not included. 

  • separately, exclusively, not together 

  • Placed separately (in regard to space or time). 

  • In or into two or more parts. 

adj
  • Having been taken apart; disassembled, in pieces. 

  • Separate, on the side. 

  • Exceptional, distinct. 

on top of that

prep
  • Also, additionally, moreover. 

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