appraise vs keep one's ears open

appraise

verb
  • To apprise, inform. 

  • To consider comprehensively. 

  • To determine the value or worth of (something), particularly as a person appointed for this purpose. 

  • To estimate; to conjecture. 

  • To judge the performance of someone, especially a worker. 

  • To praise; to commend. 

keep one's ears open

verb
  • to listen for important information. 

How often have the words appraise and keep one's ears open occurred in a corpus of books? (source: Google Ngram Viewer )