After reading a certain webcomic and seeing this phrase used to hurry someone up, I have to wonder . . .
what is the origin of the eponymous chop chop? How did this ultimate phrase of upper-class disdain come into being? And must one always clap the hands along with?
It’s from a form of pidgin English derived largely from Chinese, in the 19th century. Andrew Moody, in his article “Transmission Languages and Source Languages of Chinese Borrowings in English” (American Speech, 1996), says that “A possible source for Pidgin chop-chop is Chinese gap, ‘urgent’.”
I’ve never seen anybody clap hands when saying chop-chop. The proper thing to do is to make two rapid karate type chops with one hand while saying chop-chop. 
I seem to recall first seeing this sterotype on the TV show Bonanza . The Chinese cook, Hop Sing always seemed to be carrying around a cooking utensil (sometimes a meat clever) and would be told to “hurry up, chop-chop”.
Some years ago I posted a question on the SDMB about the phrase, “chop-chop.” I always assumed it had a racist (anti-Chinese) stigma, but other people I’ve met said no, it doesn’t. I don’t recall exactly how the answer played out, but that old thread might prove informative. I’d dig it out for you, but I’m too busy righ now.
Too busy? 
Get on with it, man!
…
Chop chop! 
Cassell’s Dictionary of Slang says it’s 19th-century Chinese pidgin and derives from the Chinese k’wâi k’wâi.
Collins English Dictionary says much the same thing except that it states the original was the Cantonese kap kap.
k’wâi k’wâi looks to me like ‘Devil Devil’ but probably those accents make it sound entirely different.
I once did a little survey, in Singapore, on the various Chinese pronunciations of Ang Mao Kwai (red headed devil (?) ) and they were all radically different.
in modern pinyin, it’s ‘kuai kuai’ or fast fast. chop chop should be a bastardized English crude approximation of the Cantonese.
Is the “chop” from the same source as in “chop suey” perhaps? I think I remember that “chop suey” is an American English term for some Chinese food leftovers made into a sort of stew and served to non-Chinese customers in Chinese restaurants on the West Coast.
I do recall that in the Chinese restaurants in Birmingham back in the 50’s that Chop Suey was on their menus. No big surprise, since they also provided fortune cookies, another non-Chinese item.
Picking nits and jacking hi (there’s one in every thread)
Who’s “Chop”?
eponymous = word derived from a specific person’s name; examples: sandwich, bowdlerize, boycott.
Chop chop as eponym? No, no.
Re the second question: I never understood “chop chop” to have anything to do with “upper class disdain;” it just means “hurry up.” At least it did in our family: “Get in the car! Chop chop!” And no hand clapping either.
I understood “eponymous” to refer to the title of the thread: “Chop chop!”
Years ago in Hong Kong, I saw an elderly Brit, resplendent in white suit, give this instruction to the man who was pulling his … rickshaw. It was straight from an old Nancy Kwan film.
A hell of a site.