At first, the sea was formed around 5.6 million years ago, due to a large-scale flood, but the waters were separated from the Atlantic Ocean by the Strait of Gibraltar, so, in the hundreds of thousands of years that followed, the water spreads dried out almost completely.
The Irish Punt was legal tender in the Republic of Ireland until 2002, when Ireland joined the Euro. This guide outlines the sources for historical exchange rates between the Irish Punt and Pound Sterling. The Irish Punt established by the Currency Act 1927 had a fixed link with Pound Sterling until March 1979.
There are records of Irish sold as slaves in 1664 to the French on St. Bartholomew, and English ships which made a stop in Ireland enroute to the Americas, typically had a cargo of Irish to sell on into the 18th century. Few people today realize that from 1600 to 1699, far more Irish were sold as slaves than Africans.