Has the account that customers use to log into Apple services always been known as an Apple ID?
I still have .mac .me &amp; .icloud addresses &amp; also one from my own domain I first registered with iTunes in maybe 2005 &amp; I don't remember it ever being called anything other than an Apple ID.
I just found this from when I joined the iTunes Store in 2005…

and this from .mac in 2004 [pictures are long gone, only text remains]

I don't have anything from earlier - I had an unfortunate break in my email storage in 2001, so have nothing older, but that probably covers it.