Great examples! My initial post is far too limited. It fascinates me, though, like etymology does, too.

'Antony' is also related to 'Antonius' (as is 'Italian Antonio').

One weird one (for me) from English is 'William' -> 'Bill' since there's no 'B' in 'William', and no 'W' in 'Bill'. I wonder what's happening there.