Apple has been using the "i" on its products for a long time now, the iPhone, the iPad, the iPod, the iMac. It's not a bad sound for a product, as opposed to calling things the Apple Phone or the Apple Pad, and it goes back to when Apple introduced a simple and inexpensive computer that was intended to help people get on that brand new thing in the 90s, the Internet.
Yep, that's what the "i" stands for. Internet. And that naming convention started in 1998, when a much less expensive computer was introduced by Apple called the iMac, which was short for Internet Macintosh. The Macintosh computer, by the way, has been around since 1984, but Apple figured that the name iMac would make people think that they could buy a simple computer mostly to surf the internet. And people did. It was very successful. I had one of those early iMacs, which had the big colorful bubble, and was sometimes referred to as "Barbie's Computer". Mine was blueberry, but you could get lots of different colors. Watch any TV show from the turn of the century and you'll see a lot of them on desks, even though businesses mostly stayed with PCs. They were colorful, and looked good on TV. And they were mostly used for personal use.
And they were easy to use, and to connect to the internet. You just plugged them in and went. I'm not really a computer guy, and even I could connect to the internet with my iMac in 1998. And, of course, the internet caught on, and is still very popular today.
When Apple introduced its music player, they called it an iPod. I suppose you could argue that it was a pod, but it certainly didn't connect to the internet. But it sounded good. And Apple kept using the "i" prefix for other stuff, like the iPhone. But really, it's all Apple.