Question: just a simple question: what does qt in bitcoin-qt stand for?

Answer: 
Qt is a cross-platform application and UI framework for developers using C++. It's is used for UI in Bitcoin-Qt. See <http://qt-project.org/>
According to the Wikipedia article:"The toolkit was called Qt because the letter Q looked appealing in Haavard's Emacs font, and "t" was inspired by Xt, the X toolkit"