What does the expression “to keep the ball rolling” mean and Where does it come from?

The host or hostess, if properly conforming with the precepts of Emily Post, “keeps the ball rolling” at a dinner party or other occasion by maintaining conversation or relating some anecdote or by providing other entertainment that will keep the interest of the guests from flagging.

The saying is of British origin, dating back to the eighteenth century, and alludes either to the game of Rugby or to the game of bandy, probably the latter.

Bandy, which is called hockey in America, dates back at least to the sixteenth century, but the puck is a small ball, even when the game is played on the ice.

Needless to say, either in this game or in Rugby, if the ball is not in motion interest in the game has certainly flagged.