obdurately vs weakly

obdurately

adv
  • In an obdurate manner; stubbornly, intractably or inflexibly. 

weakly

adj
  • Frail, sickly or of a delicate constitution; weak. 

adv
  • With little strength or force. 

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