apropos vs on high

apropos

prep
  • Regarding or concerning. 

adv
  • To the purpose; appropriately. 

  • By the way. 

  • Timely; at a good time. 

adj
  • Of an appropriate or pertinent nature. 

  • by the way, incidental 

on high

prep
  • In authority, influence, or power. 

  • To a high position; or up in, or to, the sky; above. 

  • Up in, or to, Heaven. 

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