full metal jacket

[pool]

I watched full metal jacket for the first time ever recently and it was kick ass. anyway I was wondering, how come they called the vietnamese soldiers zipperheads?

[troub]

I was able to find many sites online that gave a slang definition, most often referring to a "closed-minded" person. I don't think for a second that that's what the soldiers in the '60s meant by it. This is the only site I could find listing it as a slur towards Vietnamese AND explaining why (there were, of course, many sites listing it as an ethnic slur, but most had no explanation). I don't know if it's true or not, but it's all I could find:
http://www.asianjoke.com/others/ethnic_slurs.htm

[Max_Castle]

I always assumed it was because of the eyes, but that's just a WAG.

[Fang]

Warning: offensive racist language on following page

http://www.urbandictionary.com/define.php?term=zipperhead&f=1

[owlofcreamcheese]

I always heard it was along the lines of "you shoot them and their head head comes apart like its being unzipped"