concentrate vs hammer home

concentrate

verb
  • To focus one's thought or attention (on). 

  • To approach or meet in a common center; to consolidate. 

  • To increase the strength and diminish the bulk of, as of a liquid or an ore; to intensify, by getting rid of useless material; to condense. 

  • To bring to, or direct toward, a common center; to unite more closely; to gather into one body, mass, or force. 

noun
  • A substance that is in a condensed form. 

hammer home

verb
  • To repeatedly or continually emphasise (an opinion or idea) until or so that a person or group of people understands it. 

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