thou vs y'all

thou

verb
  • To address (a person) using the pronoun thou, especially as an expression of contempt or familiarity. 

  • To use the word thou. 

noun
  • A unit of length equal to one-thousandth of an inch (25.4 µm). 

  • A thousand, especially a thousand of some currency (dollars, pounds sterling, etc.). 

y'all

verb
  • To use the pronoun "y'all" (to). 

det
  • Your pl; y'all's 

  • The group spoken or written to. 

How often have the words thou and y'all occurred in a corpus of books? (source: Google Ngram Viewer )