主题：西河微步-学生的名字 -- 老马丁

the tradition is: short the two- or three-syllable name into one-syllable name, then add "-y" to indicate its informality.

In other Anglo-brother languages (aka. Germanic) languages, we will see similar patterns. E.g., in Dutch, it is "-j".

And "-j" and "-y" has the same pronounication in Germanic languages--anyway, their ancesters all came from the same tribe.

BTW, "willy" is used more often in UK, while "Bill" or "Billy" are used more often in States. Different English-speaking nations even diverged in informal naming.