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The OED article on 'crab', which you need to be at a university to see, clarifies that the English word is "in no way related to Latin carabus, Greek κάραβος, but to Low German krabben 'to scratch, claw'." It is, on the other hand, "allied etymologically to Middle Low German krēvet," and hence presumably to French crevette, Russian креветка 'shrimp'.
But wait! The French Wiktionary claims that crevette is a metathesis of a Norman local pronunciation of chevrette, that is 'baby she-goat', and so has nothing to do with the Germanic root.
All I can conclude is that people really like to use a [k], a rhotic, and a voiced labial obstruent in naming crustaceans, and will go to all sorts of lengths to get them in that order.
Oh yeah. I'm going to be in New York for the award ceremony and reading on the 30th at the Bowery Poetry Club. Since the time and place are posted publicly on the web, perhaps anyone who reads this is welcome to drop by. But I don't know the etiquette of such things.
Oops! I just posted my travel plans on the Internet. Anyone who tries to break into my room (which is very easy) will face the vigilance and wrath of my housemates.