It's possible that:
* You might be misremembering the name or details of the legend. There are many stories involving hounds, particularly in folklore and mythology. It could be a variation of a known legend, like the Black Shuck, a spectral hound from East Anglia, or the Barghest, a similar creature from Yorkshire.
* The "Blue Kerlew Hound" could be a local legend. It's possible this is a story specific to a certain region or community. If you can remember where you heard it, it might be easier to find information about it.
To help you find more information, could you provide any additional details you remember about the legend? For example:
* Where did you hear about it? (Specific location, book, etc.)
* What was the legend about? (Was it a friendly or dangerous creature? What did it do?)
* Were there any other details you remember? (Colors, physical traits, etc.)
With more information, I might be able to help you track down this legend.