The name means either "iron port" or "Lord's port". The "Lord" may possibly refer to the parish of the Holy Trinity (Kirk Christ Rushen). Another possibility is that the name is derived from "sheear", "westerly". The outer breakwater, visible at low tide only, was an abandoned project constructed in 1863 using the Port Erin Breakwater Railway and saw the first steam locomotive used on the island; a severe storm of 1884 later destroyed the breakwater and it was never rebuilt. Today, a marker buoy shows the extent of the breakwater, and the landward end is still clearly discernible. To the north-east, by the A7 road, are the earthwork remains of a motte-and-bailey castle known as "Cronk Howe Mooar", possibly the site of a timber fortification built by Magnus Barelegs c. 1100.