Complex sentence: The district where Nisi died was called the plain of Nisi, and, in his honour, and Saint Caillin was granted perpetual right to profits from Moynish lands as Nisi's tribute, which funded "a famous monastic settlement at Fenagh" under Gaelic Ireland.
Split into simpler sentences: The district where Nisi died was called the plain of Nisi, and, in his honour, and Saint Caillin was granted perpetual right to profits from Moynish lands as tribute. This arrangement funded "a famous monastic settlement at Fenagh" under Gaelic Ireland.