concern vs nag

concern

noun
  • A worry; a sense that something may be wrong; an identification of a possible problem. 

  • The placement of interest or worry on a subject. 

  • The expression of solicitude, anxiety, or compassion toward a thing or person. 

  • That which affects one’s welfare or happiness. A matter of interest to someone. 

  • A business, firm or enterprise; a company. 

  • Any set of information that affects the code of a computer program. 

verb
  • To engage by feeling or sentiment; to interest. 

  • To relate or belong to; to have reference to or connection with; to affect the interest of; to be of importance to. 

  • To make somebody worried. 

nag

noun
  • A persistent, bothersome thought or worry. 

  • Someone or something that nags. 

  • An old, useless horse. 

  • A repeated complaint or reminder. 

  • A small horse; a pony. 

verb
  • To bother with persistent thoughts or memories. 

  • Anyone would think that I nagged at you, Amanda! (From Amanda! by Robin Klein) 

  • a nagging pain in his left knee 

  • To repeatedly remind or complain to (someone) in an annoying way, often about insignificant or unnecessary matters. 

  • The notion that he forgot something nagged him the rest of the day. 

  • To bother or disturb persistently in any way. 

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