A name from founders William S. Harley and Arthur Davidson (whose brothers William and Walter joined the company later). But why is the Company called Harley-Davidson and not Davidson-Harley?
This was a conscious decision on the part of the founders. William S. Harley, in the very earliest days of Harley-Davidson Motor Company, was the sole, and later, Chief Engineer. It was his drafting, designing and testing that made the first motorcycles ever produced by the young company a possibility. Arthur Davidson agreed that William Harley's name should come first for this reason.
Also, the use of the hyphen designates the fact that the company was founded by two people. From time to time, a writer will refer to the company as "Harley Davidson Motor Company," which is incorrect and makes it appear that the company was founded by one person named "Harley Davidson." So now, if anyone ever asks you how Harley-Davidson got its name, you can set the record straight!