Raw prawn; ripoff

This is one of my all time favourites. I've only ever heard it used in my own country - Australia and by Australians. However, it wouldn't surprise me if it's originally Cockney or something.

For those who haven't heard it, it seems to mean 'don't try to hoodwink me' (hoodwink - there's another one), or don't try to rip me off (yet another one - rip me off).

So can anyone help with this one, or even 'hoodwink' & 'rip me off'.

Thanks,
Petalyn (yep, that's my real name, not Lotg)

From Eric Partridge, Dictionary of Catch Phrases: American and British, from the Sixteenth Century to the Present Day:
"don't come the raw prawn!" 'Don't try to put one over me!' --'Don't try to impose on me!' This catchphrase arose, during WW2, in the Australian Army; Wilkes's earliest printed date is 1942; in 1946 Rohan Rivett, 'Behind Bamboo' (a prisoner-of-war story) writes, '"Raw prawn" something far-fetched, difficult to swallow, absurd'. Apparently first dictionaried by the late Grahame Johnston, in 'The Australian Pocket Oxford Dictionary', 1976. A raw prawn is less edible than a cooked one. [Paul Beale, who edited and revised Partridge's book:] if in fact to do with cooking, then perhaps orig. a ref. to the Japanese delicacy. I have also heard the phrase used to mean 'Don't pretend to be the naive innocent!'

End of Partridge quote; back to me (R.B.): I first heard "rip off" (verb) and "ripoff" (noun) in the US, 1960s. As far as I know, they started as hippie slang.