To fall over suddenly in an uncontrolled manner. The keel is the longitudinal timber ridge along the middle of the hull to which the rest of the boat’s timbers are fixed. It acts as a counterbalance for the mast and keeps the boat stable in conditions that would otherwise cause the boat to capsize. ‘Keeled over’ referred to ships which had rolled on their side in turbulent waters and were in danger of sinking, or were laid on their side on land with their keels showing.