The team preparing Derry's Great Parchment Book of 1639 for transcription and subsequent release online has been encountering difficulties with the place names they've found in the documents.
They've an interesting blogpost about it here.
The Great Parchment Book was a survey of all the lands in County Derry/Londonderry seized by the Crown and includes names, placenames and details of rentals and contracts. It has been described as the Domesday Book of Derry. All 165 parchment pages were badly damaged in a fire at the London Guildhall back in 1786, so they have never before been studied. This project, which has carefully conserved the fragile pages, will greatly enhance our understanding of the Plantation of Ulster.