The article gets it right, but "man muss immer umkehren," is better translated as "man must always turn upside down", "inside out," "turn back" or "reverse" depending on the context.

In Afrikaans, "omkeer" is derived from the Germanic umkehren and would be used as changing direction (in a military sense) or upside down as in 'leave no stone unturned.'

Strangely, nowadays I would refer to inverting your trousers as "binneste-buite" (inside-out) or "uitkeer" in Afrikaans: roughly 'about face'.