archduke

noun

Etymology: From Middle French archeduc (modern French archiduc), from Latin archidux. Equivalent to arch- + duke.

1. The son or male-line grandson of an emperor of the Austro-Hungarian Empire.

   “World War I traditionally started with the assassination of Archduke Francis (Franz) Ferdinand.”

2. The ruler of an archduchy, in particular the Archduchy of Austria.