Confirmed these types of slang phrases emerged from the streets of north London and have travelled as far north as Manchester (maybe even further, but nobody knows what anyone is saying any further north than that.)
It's a way of making the speaker sound less vulnerable when speaking about something where emotion is required. For example, let's decipher this phrase. "Catch" refers to the way a fire would catch, or in which one would catch an illness. "Bare" means very, a lot, or lots of. "Joke" is an adjective in this case, based loosely on the word "funny." So "catching bare joke" is a less girly way of saying "oh my, I'm suffering from a case of what would be the giggles if I weren't too proud to laugh hysterically in public."
This might help, Adam: