Comment 4 for bug 666370

Making the units translatable in these dropdown boxes will be some work. It will involve /src/ui/widget/unit-menu.cpp. The use of UnitMenu relies on the text being *untranslated*; more precisely, the "get_active_text()" method of the used ComboBox should return the text untranslated. I think it is possible to use a modified ComboBox that shows a translated text in the UI, but also keeps an untranslated text for the get_active_text() method.
For exampe, have a look at how this is done for the language preference, see
"UI::Widget::PrefCombo _ui_languages" in inkscape-preferences.h, and see /ui/widget/preference-widget.
UnitMenu should be changed accordingly.