Nor' Loch was drained (creating land for today's Princes Street Gardens), and the Mound was constructed to provide a second, westerly access between the two settlements.
Nor Loch got drained
mnli hypothesis: Nor Loch got drained premise: Nor' Loch was drained (creating land for today's Princes Street Gardens), and the Mound was constructed to provide a second, westerly access between the two settlements.