anxiety vs apprehension

anxiety

noun
  • An unpleasant state of mental uneasiness, nervousness, apprehension and obsession or concern about some uncertain event. 

  • An uneasy or distressing desire (for something). 

  • A state of restlessness and agitation, often accompanied by a distressing sense of oppression or tightness in the stomach. 

apprehension

noun
  • Anticipation, especially of unfavorable things such as dread or fear or the prospect of something unpleasant in the future. 

  • Opinion; conception; sentiment; idea. 

  • The faculty by which ideas are conceived or by which perceptions are grasped; understanding. 

  • The physical act of seizing or taking hold of (something); seizing. 

  • Perception; the act of understanding using one's intellect without affirming, denying, or passing any judgment 

  • The act of seizing or taking by legal process; arrest. 

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