be kind to vs pick up on

be kind to

pick up on

verb
  • To adopt a practice in which others already engage. 

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

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

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