Dr. Brian Stowell ran a series on Manx Radio focusing on Manx Gaelic and about Manx surnames.
Of Kissack, Brian records:
"This weeks Manx surname is Kissack and Kissack comes from the Gaelic mac y Ysaig 'son of Isaac' the first written record of the name we know about in the Isle of Man dates from 1418 when it was recorded as as MacIssak (M A C I S S A K). Ballakissack in Santon was one of the centres for this family. Haughley MacIssak and Donald MacIssak took part in the rising of 1442."
Below is the audio of this radio item and it is particularly interesting as it demonstrates the correct pronunciation of the name Kissack.
Listen/download the mp3 of this text here (600kb)
With thanks to Brian Stowell and Manx Radio.