What is the origin of shaking eyes meaning surprise or fear? In a lot of shows, a character's eyes (pupil and iris) will begin to shake when they are surprised or shocked? What is the basis of this, and where was it first used?
I think it might be universal as Mysticial mentioned in the comments above, your eyes waver or tremor when you express emotions such as fear, sadness, elation etc.


  "The eyes are the window to the soul&hellip;"


I don't think it has a set origin, just one of those things that anime inherits from real life. Showing emotions in anime can be hard but not as much with some of those big doleful eyes with multiple catch lights.




  And a bit more..
  
  Eyes are an absolutely fantastic way for having your character convey
  emotions without actually saying a word. Sometimes a scene can be much
  more powerful when no words are spoken, but a character's eyes do the
  talking. This definitely happens in anime quite a lot. While most
  people think of big, bright eyes in anime, there's actually a lot more
  to it than that.