a tad vs moderately

a tad

adv
  • To a small extent; in a small amount. 

  • Very. 

  • A lot. 

  • Slightly; rather. 

moderately

adv
  • To a moderate extent or degree. 

  • In a moderate manner. 

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