What it means
Kipper can mean someone who is absolutely knackered, like a smoked fish that's had all the life dried out of it. It can also be used for a person who's a bit of a fool or who's just not with it. The exact meaning depends on context, but the image of a dried fish is always there, which is a bit grim but quite funny.
Usage examples
"After that double shift I'm a proper kipper, can barely keep my eyes open."
"Don't be such a kipper, it's obvious the bus stops here."
"He's been out in the sun all day and now he looks like a kipper."
"I feel like a right kipper after that all-nighter, my brain's turned to mush."
"He's such a kipper, he tried to pay for a bus with a library card."
Where it comes from
Kipper originally refers to a smoked herring, and the process of kippering involves curing the fish with salt and smoke until it's stiff and leathery. Over time, the word took on a figurative life in British slang: a 'kipper' could be a person who looks exhausted, as if they've been hung out to dry, or someone who's a bit of a plank. The shift from fish to person is a classic bit of British linguistic cheek, taking something ordinary and repurposing it to describe the walking dead or the half-asleep.
