This question already has an answer here:
Since Mathematica 10 every time your mouse cursor appears above some function or even variable, an annoying tooltip appears offering help:
I've become quite used to Mathematica now and I don't need these tooltips everywhere every second, and I can just as easily click the function and press F1 to get help.
I've tried almost every promising-looking option in
Edit->Preferences->Interface page, but I couldn't remove these tooltips.
So, how do I finally get rid of them?