investigate vs underseek

investigate

verb
  • To examine, look into, or scrutinize in order to discover something hidden or secret. 

  • To inquire into or study in order to ascertain facts or information. 

  • To conduct an inquiry or examination. 

underseek

verb
  • To examine; explore; investigate. 

  • To spend too little time or effort in seeking. 

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