Cahersiveen was the Poor Law Union or Civil Registration District for the Parish of Caher and the Townland Canburrin. A PLU would be no more than 12 mi. from the the townland.
What used to be would not necessarily exist today. I don't see a name for the inlet where Cahersiveen is located on a major road(perhaps a coast road)N70 from Kells to Waterville, there is a Biginish Island at the entrance to the inletwww.visitcahersiveen.ie
has maps and describes the town as
a small rural market town that has had several alternate spellings
Coolcaslagh has a recycling depot and an industrial park