Scottish folklore by Ayrshire-born Druid and Bard, Stephen G. Rae the @BardCumberland. Published by The FolkLore Press and available in print and ebook.
In lore, 'cu sìth' is the faerie dog; the size of a Highland Cow with a shaggy green coat. It will let out three barks as an ill omen:
walking in Torridon
my only companion
distant barking dog
more in my "Folklore of Scotland"