In several locations in MITK two labels for view directions are used, e.g. x (Sagittal) or x-Direction (Frontal).
The problem, as far as I see, is that it is not clearly defined inside MITK / ITK how the x-y-z axes are placed inside the body / anatomical planes.

Our render windows show the three anatomical planes (axial, sagittal, coronal) but they do not give a hint to the x-y-z-coordinates. Should we remove the x-y-z labeling / naming on the code base and solely rely on the anatomical planes?

Two examples are given here as screenshots; as you can see they even differ in their mapping of the anatomical planes to the axes:
From QmitkInteractiveTransformationWidgetControls.ui

From QmitkRegistrationManipulationWidget.ui

In the latter there are even different names for the anatomical planes used (discovered while working on T29207: Remove "Frontal" and "Transversal" as view direction from the code base).