unclear vs well-grounded

unclear

verb
  • To undo the process of clearing. 

adj
  • Not easy to see or read; indecipherable or unreadable. 

  • Ambiguous; liable to more than one interpretation. 

  • Not having a clear idea; uncertain. 

  • Not clearly or explicitly defined. 

well-grounded

adj
  • Of a person: having extensive knowledge of a subject. 

  • Of an argument, etc.: based on good judgment and solid reasoning. 

How often have the words unclear and well-grounded occurred in a corpus of books? (source: Google Ngram Viewer )