smooth operator vs voluble

smooth operator

noun
  • A person who accomplishes tasks with efficiency and grace, especially one with verbal skills who is persuasive in interpersonal relationships, negotiation, etc. 

  • A skillful, manipulative person, con artist, or clever scoundrel. 

voluble

adj
  • Fluent or having a ready flow of speech. 

  • Twisting and turning like a vine. 

  • Easily rolling or turning; having a fluid, undulating motion. 

  • Of thoughts, feelings, or something that is expressed: expressed readily or at length and in a fluent manner. 

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