The Silk Road derives its name from the lucrative trade in silk, first developed in China and a major reason for the connection of trade routes into an extensive transcontinental network. It derives from the German term "" (literally "Silk Road") and was first popularized by in 1877 by Ferdinand von Richthofen, who made seven expeditions to China from 1868 to 1872. However, the term itself has been in use in decades prior. The alternative translation "Silk Route" is also used occasionally. Although the term was coined in the 19th century, it did not gain widespread acceptance in academia or popularity among the public until the 20th century. The first book entitled "The Silk Road" was by Swedish geographer Sven Hedin in 1938.