DUKE, Dux, is also a title of honour or nobility, the next below princes.
The dukedom or dignity of duke is a Roman dignity, denominated a ducendo, "leading" or "commanding." Accordingly, the first dukes, duces, were the duces exercituum, "commanders of armies." Under the late emperors, the governors of provinces in war-time were intitled duces. In after times the same denomination was also given to the governors of provinces in time of peace. The first governor under the name of duke was a duke of the Marchia Rhætica, or Grisons, whereof mention is made in Cassiodorus; and there were afterwards thirteen dukes in the eastern empire, and twelve in the western. The Goths and Vandals, upon their over-running the provinces of the western empire, abolished the Roman dignities wherever they settled. But the Franks, &c. to please the Gauls, who had long been used to that form of government, made it a point of politics not to change any thing therein: and accordingly they divided all Gaul into duchies and counties; and gave the names sometimes of dukes, and sometimes of counts, comites, to the governors thereof.
In England, during the Saxons time, Camden observes, the officers and commanders of armies were called dukes, duces, after the ancient Roman manner,
without any addition. After the Conqueror came in, the title lay dormant till the reign of Edward III. who created his son Edward, first called the Black Prince, duke of Cornwall; which hath ever since been the peculiar inheritance of the king's eldest son during the life of his father; so that he is dux natus, non creatus. After whom there were more made, in such manner as that their titles descended to their posterity. They were created with much solemnity, per cincturam gladii, cappeque, & circuli aurei in capite impositionem. However, in the reign of Queen Elizabeth, A. D. 1572, the whole order became utterly extinct; but it was revived about 50 years afterwards by her successor, in the person of George Villiers duke of Buckingham.
Though the French retained the names and form of the ducal government, yet under their second race of kings there were scarce any such thing as dukes: but all the great lords were called counts, peers, or barons; excepting, however, the dukes of Burgundy and Aquitaine; and the duke of France, which was a dignity Hugh Capet himself held, corresponding to the modern dignity of maire de palais, or the king's lieutenant. By the weakness of the kings, the dukes or governors sometimes made themselves sovereigns of the provinces trusted to their administration. This change happened chiefly about the time of Hugh Capet; when the great lords began to dismember the kingdom, so that that prince found more competitors among them than subjects. It was even with a great deal of difficulty they could be brought to own him their superior, or to hold of him by faith and homage. By degrees, what with force, and what by marriages, these provinces, both duchies and counties, which had been rent from the crown, were again united to it. But the title duke was no longer given to the governors of provinces. From that time duke became a mere title of dignity, annexed to a person and his heirs male, without giving him any domain, territory, or jurisdiction over the place whereof he was duke. All the advantages thereof now consist in the name, and the precedence it gives.
The dukes of our days retain nothing of their ancient splendor but the coronet on their eschecheon, which is the only mark of their departed sovereignty. They are created by patent, cincture of the sword, mantle of slate, imposition of a cape, and coronet of gold on the head, and a verge of gold in their hand.
The eldest sons of dukes are by the courtesy of England styled marquises, though they are usually distinguished by their father's second title, whether it be that of marquis or earl; and the younger sons lords, with the addition of their Christian name, as Lord James, Lord Thomas, &c. and they take place of viscounts, though not so privileged by the laws of the land.
A duke has the title of grace; and being writ to, he is styled, in the heralds language, most high, potent, and noble prince. Dukes of the blood royal are styled most high, most mighty, and illustrious princes.