Is "isio" another word for wanting, or is it short for "eisiau"?
The word is eisiau ('need' or 'want'). It is pronounced in various different ways in different parts of Wales and these phonetic spellings are often used informally instead of eisiau. So you may see isio, isha, isia, eisia, eisha, and so on.
Thank you. That's very helpful!
It's another form of eisiau - isio is used more in the north, I believe, and closer to how they actually pronounce that word there in the everyday spoken language, while eisiau is the "standard" form.