yea vs yessum

yea

noun
  • An affirmative vote, usually but not always spoken 

intj
  • Yeah, right, yes. 

adv
  • Thus, so (now often accompanied by a hand gesture by way of measurement). 

yessum

abbrev
  • yes ma’am (also used, somewhat less commonly, when speaking to a man) 

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