http://www.skyhunter.com/marcs/petnames/IntroPetNames.html
A pentane system actually protects you from phishing attacks and you don't really share your pentanes. You can use your petname as a nickname when introducing a key to someone else. One of the most important parts is to have a good UI/UX that does not confuse nicknames with pentanes or allow you to accidentally accept a nickname as pentane that is confusingly close to an already existing petname.
Nicknames are names that you propose using when introducing yourself or someone else. A pet name is the name you assign privately. So Lumberg could be a nickname but your petname might be "dickhead boss". You're free to introduce him to people you know either way you'd like.