Let’s start with the basics: The numbers 8-9-3 essentially mean yakuza. Like so much in Japanese language, it derives from word play. In the card game oicho-kabu (similar to the Western blackjack), the object is to amass three cards that add up to a number ending in nine. Therefore, 19 is the best score, while 20 is the worst possible score.
So do the math. An unfortunate hand consisting of an eight (ya), nine (ku), and three (za) adds up to 20. Yakuza members have always considered themselves losers, or outcasts, and thus the name stuck.
In my book Tokyo Lives, the meaning is elucidated in this passage:
“Ice deals a round to the contestants, including Pig Face. Cards shuffle and pass through sweaty palms, but finally the players showcase their hands. Pig Face busts with a 20, displaying a hand of 8-9-3, or ya-ku-za in slang. Chewing on his cigarette, Ice reveals a sum of 19, and roars with laughter as he collects money from the others. ‘How fitting,’ he snarls as he makes a show of raking in Pig Face’s money. ‘A worthless score from a worthless human. You were meant to be a gangster!’”