no really vs sincerely

no really

adv
  • really; seriously; used to attempt to introduce a serious point in a less serious conversation 

intj
  • no kidding!; is that so? (sometimes used sarcastically in response to the obvious) 

sincerely

adv
  • In a sincere or earnest manner; honestly. 

  • A conventional formula for ending a letter, used when the salutation addresses the person for whom the letter is intended by his or her name. 

How often have the words no really and sincerely occurred in a corpus of books? (source: Google Ngram Viewer )