As to the nickname - I'm working on this theory that a name to an angel is attached to the way they project themselves, so others started calling Castiel 'Cas' because he sort of adopted the name/personality from Dean and so when other angels saw him they, um, SAW him as 'Cas' as opposed to Castiel. If that makes sense? Like the name was part of his aura or something and that physically changed when he started to think of himself as 'Cas.' Bah, I like the idea anyway :p
I am with you on this. I mean, it's not like the angels are speaking English. They haven't been to Earth in 2000 years. I think they communicate in some other way than speach, really, but it just comes out that way when they are in bodies and if their bodies spoke Chinese, that would be the default, you know? So it's kind of like their names are not words so much as who they are for themselves like an LJ name, and when Dean started calling him Cas, that's who he thought of himself as and thus, like changing your LJ name, it just shows up that way everywhere and nobody even notices they're doing it because it's all the same to them.
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I am with you on this. I mean, it's not like the angels are speaking English. They haven't been to Earth in 2000 years. I think they communicate in some other way than speach, really, but it just comes out that way when they are in bodies and if their bodies spoke Chinese, that would be the default, you know? So it's kind of like their names are not words so much as who they are for themselves like an LJ name, and when Dean started calling him Cas, that's who he thought of himself as and thus, like changing your LJ name, it just shows up that way everywhere and nobody even notices they're doing it because it's all the same to them.