The most likely German candidate would be 'sonst', which would be both in common use and short enough for a programming language keyword. E.g. the most likely option for 'if-then-else' is 'wenn-dann-sonst', assuming that German-origin theory is right of course.
One thing that's mostly forgotten today is that German had a very rich 'corpus' of wonderful nerdy computer science words up until the 1990s which unfortunately has fallen out of fashion. Nowadays it's a pretty terrible 'pidgin dialect' when Germans talk about programming and computers to each other (to a point where it's much less awkward to just speak English in the first place lol).
As a non-native speaker of both English and German, I feel a little difference in usage. I liked this bit of slop:
‘The most significant nuanced departure is that "sonst" can mean "normally," "usually," or "in general," contrasting a specific event against a baseline of normality. "Else" cannot do this.’
There is an etymological root to ‘sonst’ that is also the root of English ‘thus’. The German explanation would fit well in this story (but indeed no evidence presented).
I worked on a GIS system in a german speaking company, it was very confusing, it was mostly programmed in english, apart from the things we we’re modelling, which had extremely specific and often long german names.
Not sure what the original German version was, but
falls-dann-sonst
would be more correct, since "wenn" is temporal, like the English "when".
Many Germans often use these wrongly in everyday speech, but mathematicians like Friedrich L. Bauer probably wouldn't.