[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.)

[anthk]

Spanish too. Francisco Javier -> Javi, or maybe Paco (Francisco), but Javi would be the obvious case.

Francisco -> Paco from Saint Francis holding a Pater Comunitatis title in Latin.

But, as a weirder case:

José María -> Chema

Luis María -> Luisma

Juan Manuel -> Juanma

José Manuel -> Chema/Josema

Juan Ramón -> Juanra

María José (women's name) -> Marijose

[walthamstow]

My personal favourite is Juan Carlos -> Juanca. Sounds great in British English.