meditation vs pondering

meditation

noun
  • A devotional exercise of, or leading to contemplation. 

  • A contemplative discourse, often on a religious or philosophical subject. 

  • Careful and thorough thought. 

  • A musical theme treated in a meditative manner. 

pondering

noun
  • An act of rumination or cogitation. 

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