The name Darrah indicates an allied family of the Scottish Clan Donald. The Darrah name originated from the Gaelic “Dair” meaning Oak, and the earliest members of the family lived on the Scottish islands of Islay and Jura in the southeast county of Argyl.
Being lowlanders many members of the Darrah family undoubtedly migrated to Ulster during the Plantations of the 17th century, locating mainly in Glenarm Parish of County Antrim and becoming part of the immense Presbyterian resettlement of that area.
When the English turned against the Ulster Scots in the 18th century, a number of the Darrahs probably migrated to the American Colonies, concentrating mainly in New Hampshire and Pennsylvania. Nearly every Darrah immigrant that I have found who arrived in the Colonies prior to or immediately after the Revolution came from County Antrim.
Several great waves of Ulster migrations occurred prior to the American Revolution, and I speculate that our particular Darrah branch landed in Philadelphia in the mid-18th century.