babbling vs running on at the mouth

babbling

noun
  • A confused murmur, as of a stream. 

  • a stage in child language acquisition, during which an infant appears to be experimenting with uttering sounds of language, but not yet producing any recognizable words 

  • Idle senseless talk; prattle. 

  • sounds produced by infant during the babbling period 

running on at the mouth

How often have the words babbling and running on at the mouth occurred in a corpus of books? (source: Google Ngram Viewer )