smoothen vs walk through

smoothen

verb
  • To become smooth. 

  • To make smooth. 

walk through

verb
  • To perform (something) with ease or perfunctorily. 

  • Used other than figuratively or idiomatically: see walk, through. 

  • To explain (something) to (someone), step by step. 

  • To rehearse (something) casually. 

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