hrm vs mmm

hrm

intj
  • Expresses a moment of particular curiosity or thoughtfulness. 

mmm

intj
  • An expression used to show thought or reflection 

  • Used to represent an utterance that is muffled or spoken with a full mouth (also spelled "mmph"). 

  • Yes. 

  • An emotional expression of contentment 

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