I've heard the phrase so many times, but only now am wondering where it comes from.
I know it is used to mean that someone has been tricked, or has in some way fallen for a trap.
e.g.
Bob: So I ended up buying the volcano insurance from the salesman in the end.
Geoff: Wow! He stitched you up like a kipper.
But what on earth have "kippers" got to do with anything?
I think it's a mixture of similes. He may have stitched you up, or he may equally have done you. In the latter case, he may have done you brown (like a piece of meat is well done) or done you like a kipper (even more so, since kippers are done, or smoked, for many hours). Combining the two is a jocular turn of phrase (like without a paddle to stand on) that is easily picked up by people looking for a strong or picturesque phrase without worrying much about its origins.
Edit: I notice (e.g. here) that done up like a kipper is also widely used. The problem with criminal argot of this era is "Minder", and the Godfather Effect; it is probably impossible now to disentangle which phrases were in use in the 70s/80s and picked up by the scriptwriters, and which were invented for effect by the scriptwriters, and picked up by the wide boys of South London or Essex.
I'm not convinced it's a "mixture of similes". I can't find any relevant references to like a kipper prior to about 1970, and I think when it did come in about then, it started as South London slang.
So I'm inclined to credit the explanation given here, that it's a reference to the the extra wide tie called the 'kipper' that became popular around then. Thus called partly because the original designer was Michael Fish, and partly because of the tie's shape.
On the metaphorical allusion to kippers the foodstuff, I'd note that they're pretty unrecognisable as "fish" once they've been split and smoked. They've been well and truly done over.
Also note that to have a stitch on someone was (now obsolete) British slang for to bear a grudge. Which is probably where the later slang stitch someone up came from (it means to "frame" someone - falsely make it appear they're guilty).
OP's more general definition (to trick someone) is increasingly common lately, but I think with or without "kipper", most usages still relate to being (usually falsely) made to appear guilty.
My mate cockney Mick is proper old skool, he used to say" he done me up a kipper"/ I asked him what it meant and he said in the old days they used to gut fish and stitch em back together again, so basically it meant you'd been stitched up. We used to play all sorts of pranks on each other at work an he'd always come out with that phrase when we'd "stitched him up".
Fish are gutted then spit into two parts lengthways, before smoking. The two parts are packaged together for sale. In Britain, between the wars, seamstresses were in demand and frequently moved to new employers. It was unusual for them to move without their friend, so seamstresses usually came in pairs and were referred to as kippers. Seamstresses stitch. ‘Stitched like a kipper’ is a whimsical development of ‘stitched up’. I am unable to verify the explanation. It is dredged from the banks of my mind.
Stitched up means framed, put in the bag and stitched up so tight so you can't get out of the bag or the frame. It's not just that someone framed you, but it's a tight frame and you're trapped with no way out.
Kippers are usually opened up, not just gutted like most fish. So you are not only fooled, but you are opened up and made vulnerable.
Chiming in on the "stitched up" phrase here - I believe "Stitched up" as a phrase on its own means that you've been found out or discovered trying to get away with something - and originates from navy sailing ships. Or so I was told by an enthusiastic tour guide on HMS Victory. A sailor would be buried at sea by being sewn into the hammock he slept in, and thrown overboard. Sometimes sailors would try to jump ship by faking death and taking their chances in the sea. But traditionally the final stitch is put through the corpses nose. (Apparently because this was once done by accident and the "corpse" sat up, and turned out to be a sailor who had gone into a catatonic coma - but perhaps it was done to prevent deserters?) Thus if you were faking it and alive, you'd be "stitched up" by the final stitch going through your nose and presumably giving the game away...! "Sewn up" is also a (rarely used) term for being drunk (meaning you're so useless you might as well be sewn into your hammock and thrown into the sea). I imagine neither of those have anything to do with Kippers....
To stitch up is similar to snitch but with false information.
As for the kipper; it could be metaphorical; or what about, "to be stitched up like Yom Kippur" ;)
