These are shouts of communication between gondoliers. Their literal meanings have to do with how the oars are to be stroked. In effect they are the shouted equivalent of turn-signals on a car and indicate how the boats are to be maneuvered. For example, if a gondolier sees a gondola on a course that threatens a head-on collision with his own boat, he might shout “Premé!” which means each boat should be veered to the left and so pass one another right side to right side. Conversely, “Stalì!” means veer right and so pass left side to left side. The words have somewhat different implications in other situations, but we needn’t go into them here. This information is based on writings of John Ruskin (259).