[wongarsu]

Same in Germany, just that we usually call it ground floor instead of 0th floor.

You could argue it's a bit of a translation error. The French and German words for floor are referring to ways to add platforms above ground. Either by referring to walls, wooden columns or floor joists. Over the course of language evolution those words have both broadened and specialized, referring to building levels in general. But the way they are counted still reflects that they originally refer to levels built above ground. The English "floor" on the other hand counts the number of levels that are ground-like, which naturally starts at the actual ground.

[mathieuh]

It’s the same in non-American Anglo countries as well. Zero-indexed with the zeroth floor being called “ground”.

[fecal_henge]

In my (physics faculty) building 0 is the lowest floor. 2 is ground level.

I used to work in Civil Eng which started at either G or 0.

[AndrewSwift]

A good observation that explains everything!