lock lips vs osculate

lock lips

verb
  • To kiss on the lips; to engage in a French kiss. 

osculate

verb
  • To kiss. 

  • To form a connecting link between two genera. 

  • To make contact. 

  • To touch so as to have the same tangent and curvature at the point of contact. 

  • To perform osculation. 

adj
  • Relating to kissing. 

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