According to this article, the i stands for "internet" because, back in 1998 when the iMac was released, a computer which had the built-in ability to connect to the Internet was pretty radical, as was spelling Internet with a lower case i.
https://www.howtogeek.com/784151/what-does-the-i-in-iphone-stand-for/
https://www.howtogeek.com/784151/what-does-the-i-in-iphone-stand-for/