in the can

1. In the lavatory, as in He can't come to the phone; he's in the can . The related on the can means “sitting on the toilet.” The noun can is used for both the room and the toilet. [ Slang ; c. 1900]

2. As an out-of-the-money finisher in a horse race, where a horse comes in fourth or worse. For example, He had no luck that day—every bet ended up in the can . [1960s]

3. Completed, as in About a hundred pages of her next book are in the can . This usage originated in filmmaking to describe a completed motion picture, when film was literally put into a can or canister. [ Slang ; c. 1930]