later on vs latter

later on

adv
  • At some time in the future; subsequently; later. 

latter

adj
  • In the past, but close (or closer) to the present time. 

  • Relating to or being the second of two items. 

  • Near (or nearer) to the end. 

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