Oh, please, can't we get real about the virtuous and amiable Dogons?
To my knowledge, the origins of Sirius are unknown, and are unlikely to have anything to do with
Cyrus.
As for Sirius Black in the HP books, he's able to change his human shape to that of a dog. And Sirius is - ta-daah - the Dog
Star. So JK Rowling used it for a good, comic reason. When I was a child I read a delightful book about a performing
Scottie whose stage name was Sirius - same reason - though for everyday use he was
Garry.