come the raw prawn

Etymology
From World War II military slang. Construction obscure; suggestions are:
 * From + the +  +  — thus, to attempt to deceive by feigning ignorance.
 * From + the + raw prawn = something hard to swallow.

Verb

 * 1)  To attempt to deceive or impose upon (someone).
 * 2) * 1951, Dymphna Cusack, Florence James, 1957, Come In Spinner, |%22comes+the+raw+prawn%22|%22coming+the+raw+prawn%22|%22came+the+raw+prawn%22+-intitle:%22%22+-inauthor:%22%22&dq=%22come+the+raw+prawn%22|%22comes+the+raw+prawn%22|%22coming+the+raw+prawn%22|%22came+the+raw+prawn%22+-intitle:%22%22+-inauthor:%22%22&hl=en&sa=X&ei=SogvT6HcIOiSiAeT083SDg&redir_esc=y page 306,
 * “Coupla bastards come the raw prawn over me on the last lap up from Melbourne and I done me last bob at Swy.”

Usage notes

 * As the citations attest, this phrase is often used in the negative, e.g. "Don't come the raw prawn [with me]!", i.e. do not feign innocence. The phrase may also be abbreviated, giving "Don't come the raw!"