[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.