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I doubt there's a proper name for it, but try sleeves, wrapping, words like that. And check ebay.
 
It's likely some sort of cut to size poly tubing of sorts. Search uline.com for similar products.
 
Why do you need to know? Are you writing a master's dissertation on them?

OP: "Professor, I don't know what to do my dissertation for my degree in Stuff Apple Makes. Can you offer any ideas?"

Professor: "Well you could try doing it on those things that Apple uses in their packaging. You know the plastic sleeve things that go on cables and stuff. You should be able to get a hundred pages on that. Oh and try to find out what they're called."

OP: "That's a great idea! By the way, MacRumors.com is considered a valid research source by the university, right?"
 
OP: "Professor, I don't know what to do my dissertation for my degree in Stuff Apple Makes. Can you offer any ideas?"

Professor: "Well you could try doing it on those things that Apple uses in their packaging. You know the plastic sleeve things that go on cables and stuff. You should be able to get a hundred pages on that. Oh and try to find out what they're called."

OP: "That's a great idea! By the way, MacRumors.com is considered a valid research source by the university, right?"

Good heavens I hope my sarcasm came through in my first post.

OP you could also email Steve Jobs. If it's a short response, he might respond. "Dude, just call them sleeves. Not that big a deal."
 
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