Eugene tells me that 'Hornby' is derived from the Coast Salish for Hole in the Sky, an allusion to an asserted local weather phenomena where the island remains sunny and dry while rain falls around it. Wikipedia tells us that the Pentlatch, a Coast Salish First Nations band, called the Island Ja-dai-aich, meaning The Outer Island. The Spanish renamed it in 1791, to Isla de Lerena, after the Spanish Finance Minister. The British renamed it again in 1850, after Rear Admiral Phipps Hornby, then Commander of the Pacific Station.
I think Eugene, handsome older gentleman that he was, might having been pulling my mainlanders leg.