Петечка

What's Петечка short for?
Заранее большое спасибо!!

Петр (Петя) Петечка очень ласково звучит

It's a diminutive from Петя wich in it's turn a diminutive from Пётр. Only a mother could call like this her little son or a girl could call so her lover too. If a guy call like this another guy whos name is Пётр, that would be an insult.