stammer vs stutter

stammer

verb
  • To keep repeating a particular sound involuntarily during speech. 

  • To utter with a stammer, or with timid hesitancy. 

noun
  • A speech defect whereby someone speaks with a stammer 

  • The involuntary repetition of a sound in speech. 

stutter

verb
  • To speak with a spasmodic repetition of vocal sounds. 

  • To exhaust a gas with difficulty 

noun
  • A speech disorder characterised by stuttering. 

How often have the words stammer and stutter occurred in a corpus of books? (source: Google Ngram Viewer )