difficulty vs shifter

difficulty

noun
  • That which cannot be easily understood or believed. 

  • Physical danger from the environment, especially with risk of drowning 

  • An obstacle that hinders achievement of a goal. 

  • The state of being difficult, or hard to do. 

  • An objection. 

  • An awkward situation or quarrel. 

shifter

noun
  • A word whose meaning changes depending on the situation, as by deixis. 

  • A switcher or shunter: a railroad locomotive used for shunting. 

  • One who, or that which, shifts or changes. 

  • An assistant to the ship's cook in washing, steeping, and shifting the salt provisions. 

  • A component used by the rider to control the gearing mechanisms and select the desired gear ratio, usually connected to the derailleur by a mechanical actuation cable. 

  • An arrangement for shifting a belt sidewise from one pulley to another. 

  • A genre of erotica focusing on lycanthropes or other shapeshifters, such as werewolves. 

  • A spanner with an adjustable jaw size. 

  • A person who changes the reality their consciousness resides in, through meditation or other means. 

  • A wire for changing a loop from one needle to another, as in narrowing, etc. 

  • A person employed to repair the horseways and other passages, and keep them unobstructed. 

  • A shape-shifter, or a person or other being capable of changing their physical form. 

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