Replies
The abb. for Jonathan is actually Jon/Jnthn
I've got a couple of links that provide a list of abbreviations.
http://www.genealogyintime.com/dictionary/list-of-first-name-abbreviations.html
https://en.wiktionary.org/wiki/Appendix:Abbreviations_for_English_given_names
http://familyhistory.byu.edu/Downloads/BritishNames.pdf
I've got a couple of links that provide a list of abbreviations.
http://www.genealogyintime.com/dictionary/list-of-first-name-abbreviations.html
https://en.wiktionary.org/wiki/Appendix:Abbreviations_for_English_given_names
http://familyhistory.byu.edu/Downloads/BritishNames.pdf