There is no tooltip set in the code shared. If you are seeing one, then it is set somewhere else - code that is not shared in the question. Check against the actual code in the Page or View or in the code-behind.
Update
Why not simply work with the
ToolTipService
and the
IsEnabled
property. Example:
<TextBox Text="Is Enable Test" Width="100"
ToolTipService.IsEnabled ="{Binding ElementName=EnabledState, Path=IsChecked}"
ToolTipService.ToolTip="This is a tooltip for the textbox"/>
<CheckBox x:Name="EnabledState" Content="Show Tooltip" IsChecked="True" Margin="10 0" />