Perhaps people mistook Dan Brown as authoritative on the matter. I browsed the read samples of some of the top listed books on Leonardo da Vinci on Amazon, and

Perhaps people mistook Dan Brown as authoritative on the matter. I browsed the read samples of some of the top listed books on Leonardo da Vinci on Amazon, and all use "Leonardo" in their introduction whenever they do not refer to him as "Leonardo da Vinci". I found no single isolated "da Vinci". See: https://www.amazon.com/-/en/dp/0715324535 https://www.amazon.com/-/en/dp/0715324535 https://www.amazon.com/-/en/dp/B0DHFRBMF3 https://www.amazon.com/-/en/dp/B0DHFRBMF3 https://www.amazon.com/-/en/dp/1501139169 https://www.amazon.com/-/en/dp/1501139169 The standard way to avoid confusion is to introduce him as "Leonardo da Vinci" and later just say "Leonardo".