encumbrance vs logrolling

encumbrance

verb
  • To apply an encumbrance to (property, etc.). 

noun
  • An interest, right, burden, or liability attached to a title of land, such as a lien or mortgage. 

  • Something that encumbers; a burden that must be carried. 

  • One who is dependent on another. 

logrolling

noun
  • The act of balancing on a log floating on a river to guide it downstream, often involving rolling it using one's feet; birling. 

  • Mutual recommendation of friends' or colleagues' services or products, such as book recommendations in literary reviews. 

  • The rolling of logs from one place to another; an occasion when people meet to help each other roll logs. 

  • A concerted effort to push forward mutually advantageous legislative agendas by combining two items, either or both of which might fail on its own, into a single bill that is more likely to pass. 

  • A sport in which two people balance on a log floating in a body of water, each one aiming to cause the opponent to fall off by rolling or kicking the log. 

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