dither (v.)

"to shake, tremble," 1610s, perhaps a variant of dadder, from Middle English daderen "to quake, tremble" (mid-14c.) a frequentative formation on a pattern similar to totter, patter, etc. Wedgwood points to a large group of similar words signifying motion to and fro, including dither, diddle, dandle, toddle, doddle ("shake the head," 1650s). Related: Doddered; doddering.