The beginning of counting down for someone to chug their
beer, or drink they must drink. And if the whole thing is sung and they haven't finished their drink then they don't deserve to be at your party.
(The full P.C. phrase: Down in
One! , Down in
One, Down in One, Down in Two, Down in Two, Down in Two, Down in Three, Down in Three, Down in Three, Down in Four ... You're a Bore, Why are we waiting we could be masterb*
ting, Drink MF, Drink MF Drink!)