unfounded vs ungrounded

unfounded

adj
  • Having no strong foundation; not based on solid reasons or facts. 

  • Not having been founded or instituted. 

ungrounded

adj
  • Not grounded; without ground or basis, unreal, false. 

  • Not connected to ground potential 

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