pick up on vs unearth

pick up on

verb
  • To notice, observe, learn, or understand, especially something otherwise overlooked. 

  • To adopt a practice in which others already engage. 

  • To continue or build upon (for example, a task, analysis, or narrative), beginning from a point at which someone has previously stopped. 

unearth

verb
  • To uncover or find; to bring out from concealment 

  • To drive or draw from the earth. 

  • To dig up. 

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