<Tr> <Td> <Ul> <Li> </Li> <Li> </Li> <Li> </Li> </Ul> </Td> </Tr> <Ul> <Li> </Li> <Li> </Li> <Li> </Li> </Ul> <P> A duke (male) or duchess (female) can either be a monarch ruling over a duchy or a member of royalty or nobility, historically of highest rank below the monarch . The title comes from French duc, itself from the Latin dux,' leader', a term used in republican Rome to refer to a military commander without an official rank (particularly one of Germanic or Celtic origin), and later coming to mean the leading military commander of a province . </P> <P> The title dux survived in the Eastern Roman Empire where it was used in several contexts signifying a rank equivalent to a captain or general . Later on, in the 11th century, the title Megas Doux was introduced for the post of commander - in - chief of the entire navy . </P>

Where do the duke and duchess names come from