I was an ICQ user but I haven't logged in since the early 2000s I would guess? I have a faint recollection of maybe using Trillium during its heyday with ICQ maybe in the 2003-2004 time period?

Really? My impression was 2 decades ago it was pretty popular, at least lots of my high school mates used it.

I never, and eventually picked YM instead few years later.