Dammit Jim!

It's called the Bluenose Marathon because of the Bluenose, a famous fishing/racing schooner from Nova Scotia (the sail boat on the Canadian dime). The ship was named Bluenose because it was a nickname for Nova Scotians. Nova Scotians were apparently called bluenoses because they liked to wear blue sweaters and would wipe their nose on their sleeves while working at sea and die their nose blue.