A common form "what does that have to do with the price of tea in China?", is a retort to an irrelevant suggestion. This facetious usage implies that the topic under discussion might as well be the price of tea in China for all the relevance the speaker's suggestion bears on it.
Suzie: I love my new skirt!
Anne: I know! I love my new shirt!
Beth: Look at this hot guy on my phone!
Suzie: What does that have to do with the price of tea in China?
"What does that have to do with the price of tea in China?" is an expression which denotes that what the other person justsaid is completely unrelated to the original topic.
Person A: President Bush is the best president EVER!
Person B: No, he's not! He's the worst president!
Person A: Why do you say that?
Person B: Umm, I just bought a guitar.
Person A: Well, what does that have to do with the price of tea in China?
A small piece of information. Derived from the word ken, used often in the scottish language and is synonymous with knowledge.
Person 1: "Hey I don't get this shit. How do you solve this problem?"
Person 2: "I got that one. Give me some kenlets on this assignment and I'll help you w/ that one."