Comment by bityard

Tangent:

My father's family is German and all of the males in the family only used their middle name for everything except legal and financial documents. For example, Carl Hans Schmidt (to pick a semi-made-up example) would introduce himself as Hans to everyone he met, and the family would refer to him as Hansi.

I always wondered if that was a German (or regional) tradition, or a fun family quirk.

(The males have all regrettably passed on but I asked my aunts once and they said they had no idea why or how that was a thing, that's just what they did.)