investigate vs swot up on

investigate

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

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

  • To conduct an inquiry or examination. 

swot up on

verb
  • To study particularly hard to learn a subject quickly. 

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