mindmap
root((结巴))
stammer
implies a temporary inhibition from fear, embarrassment, or shock: ~ed his thanks, overcome with embarrassment.
stutter
is likely to suggest a habitual defect characterized by repetition of sounds, but it may apply to a similar manifestation due to a temporary cause: ~s when excited; or even, as may stammer, to something suggesting the pattern of a stutterer: the engine ~ed then came to life.