if only vs provided

if only

conj
  • Used other than figuratively or idiomatically: see if, only. 

  • I wish that; signifies a wish or desire for the present or the future. 

  • I wish that; signifies a regret about an action in the past. 

  • Even if for no other reason than; only just. 

provided

conj
  • Only if (the stipulation that follows is true). 

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