I thought it came from when there's police going by you tell people to keep their heads at 12. Don't look at them or they'll accuse you of being "suspicious" and want to detain you and run your ID for warrants etc
I didn't learn this until I heard Post Malone/HARDY's "Hide My Gun" with the lyric, "If the three times four's banging at our door, would you stall and let me slip out the back?"
Which overall the whole song almost works as a Luigi theme song.