Dither

dither \ˈdi-thər\ intransitive verb: 1. shiver, tremble, 2. to act nervously or indecisively; vacillate
noun: a highly nervous, excited or agitated state; excitement, confusion

Etymology: Middle English didderen

Dither is also a scientific term. Explore it here on Wikipedia, and make sure you read the fascinating quote from Ken Pohlmann’s Principles of Digital Audio in the subsection “Origin of the word ‘dither.’”