What's the Deal with T-shirts with Random, Gibberish Japanese Writing on Them?

The Brainfood Show:

Browse any clothing store and you’ll more than likely find at least one t-shirt covered in characters using the Japanese writing system. And if you can actually read Japanese, you’ve probably noticed that what’s written is often gibberish. Rather interestingly, the reverse is also popular in Japan, where one can find many a t-shirt with random English words instead. So how did this all start and why isn’t anyone bothering to check the meanings?

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