The Devil's Tattoo...
It's not something injected into skin with a needle. It's a knock. dat dah duh dit dit.. dat! dat! Wordwise: "Shave and a haircut -- two bits." Versions of it become a "secret" knock so a girl knows it's her lover at the door. Or a secret agent uses it to gain admittance to a listening post. Or it... Sign in to see full entry.