At the Gold panel at [[Salute to Supernatural Seattle 2017]] [https://twitter.com/fangasmspn/status/851141195312922624?lang=en Jared revealed] that "Nesnej" is what Jensen's friends call him when he's had too much bourbon!
Nesnej is Jensen spelled backward and pronounced NES- NEG with a soft g. It is used in fandom to refer to Jensen when he is drunk or just generally being goofy. eg "I wodner wonder if we will get Nesnej at the panel today".
* [https://www.youtube.com/watch?v=gWxh3kzGBTU Watch the panel here staring at 2:40s]