I am embarrassed to say I knew neither the original nor the aeronautical meaning of the word leeway. It is extraordinary how much of pirate lore comes from this book. Also, although written in 1881 close to the time of the discovery of the tubercle bacillus, Stevenson either still believed in the miasma theory or he put it in the mouth of his 18th century Dr. Livesey for historical verisimilitude (unlikely).