means To speak with involuntary repetitions or prolongations of sounds and pauses, disrupting the smooth flow of words.

from From an old Germanic root meaning to push, knock, or strike against — the same family that gives us 'stoßen' in German. English 'stutter' is a frequentative of an earlier verb 'stut' (to stutter), with that '-er' ending suggesting the repeated, knocking motion: speech bumping again and again against the same closed door. A cousin of 'stammer,' which travels a parallel path.