drive home vs harp on

drive home

verb
  • To emphasize (a point) with tangible or powerful demonstration. 

  • Used other than figuratively or idiomatically: see drive, home. 

  • To push something into position completely by force. 

harp on

verb
  • To nag about; to complain incessantly or persistently request; to continue to bring up as a point of contention. 

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