drop a line to vs get on to

drop a line to

get on to

verb
  • Used other than figuratively or idiomatically: see get on, to. 

  • To contact (someone) in order to raise or discuss a certain matter. 

  • To progress to; to start working on. 

How often have the words drop a line to and get on to occurred in a corpus of books? (source: Google Ngram Viewer )