arguably vs possibly

arguably

adv
  • As can be supported or proven by sound logical deduction, evidence, and precedent. 

possibly

adv
  • Perhaps; indicates that the proposition may be true (is not certainly false) regardless of any facts or circumstances known to, stated by or implied by the speaker. 

  • In the realm of possibility; indicates that the action may successfully be performed (is not impossible) regardless of any facts or circumstances known to, stated by or implied by the speaker that might limit the performance. 

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