x-gtk-use-system-tooltips

x-gtk-use-system-tooltips is a variable defined in `C source code'.
Its value is

t

Documentation:
If non-nil with a Gtk+ built Emacs, the Gtk+ tooltip is used.
Otherwise use Emacs own tooltip implementation.
When using Gtk+ tooltips, the tooltip face is not used.

You can customize this variable.

This variable was introduced, or its default value was changed, in version 23.3 of Emacs.