A phrase used to answer or address anything. Swallow meaning the species of bird. The term makes no sense whatsoever, but it does have its uses. Best used when people don't know what to say or as a way to trash talk someone.
Person 1: "Dude, don't be an asshole."
Person 2: "Feed the swallow."
Person 1: "On a scale of 1 to 10, how do you feel?"