encumber vs enlighten

encumber

verb
  • To burden with a legal claim or other obligation. 

  • To load down something with a burden. 

  • To restrict or block something with a hindrance or impediment. 

enlighten

verb
  • To make something clear to (someone); to give knowledge or understanding to. 

  • To supply with light. 

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