Listen closely. The word ⑨ originated from the 1986 movie Hustler 2, from the nine ball in billiards.
If you don't keep up with your studies, people will call you stupid. Promise me you'll stop playing games all the time and do your studying, ok?
⑨? What are you talking about?
What? You want something?
In fact, there's a famous parody of it - the Armored Core 'Nine Ball', piloted by Hustler One. A plastic model of Nine Ball's final form, Nine Ball Seraph, just came out recently, you should check it out.