Question: What title was created by Frederick I, Holy Roman Emperor?

Context articles: Duke of Brabant
Eleanor of Portugal, Holy Roman Empress
Constance, Queen of Sicily
Gerasim Zelić
Karl Anselm, 4th Prince of Thurn and Taxis
Frederick I, Holy Roman Emperor
List of monarchs of Prussia
German Emperor
Concordat of Worms
List of Holy Roman Empresses

The Duke of Brabant was formally the ruler of the Duchy of Brabant since 1183/1184.
 The title was created by the German Emperor Frederick Barbarossa in favor of Henry I of the House of Reginar, son of Godfrey III of Leuven (who was Duke of Lower Lotharingia at that time).
 The Duchy of Brabant was a feudal elevation of the since 1085/1086 existing title of Landgrave of Brabant.
 This was an Imperial fief which was assigned to Count Henry III of Leuven shortly after the death of the preceding Count of Brabant, Count Palatine Herman II of Lotharingia (born 20 September 1085).
 Although the corresponding county was quite small (limited to the territory between the rivers Senne and Dender) its name was applied to the entire country under control of the Dukes from the 13th century on.
 In 1190, after the death of Godfrey III, Henry I also became Duke of Lotharingia.
 Formerly Lower Lotharingia, this title was now practically without territorial authority, but was borne by the later Dukes of Brabant as an honorific title.
Eleanor of Portugal (18 September 1434 – 3 September 1467) was Empress of the Holy Roman Empire.
 A Portuguese "infanta" (princess), daughter of King Edward of Portugal and his wife Eleanor of Aragon, she was the consort of Holy Roman Emperor Frederick III and the mother of Holy Roman Emperor Maximilian I.
Constance (2 November 1154 – 27 November 1198) was Queen regnant of Sicily in 1194–98, jointly with her spouse from 1194 to 1197, and with her infant son Frederick II, Holy Roman Emperor, in 1198, as the heiress of the Norman kings of Sicily.
 She was also Holy Roman Empress by marriage to Henry VI, Holy Roman Emperor.
Gerasim Zelić (Serbian: Герасим Зелић ; 1752–1828) was a renowned Serbian Orthodox Church archimandrite, traveller and writer (a contemporary and compatriot of Dositej Obradović).
 His chief work is "Žitije" (Lives), in three volumes.
 They are memoirs of his travels throughout western Europe, Russia and Asia Minor from the latter half of the 18th century to the first decade of the 19th century and the famous personalities (Napoleon, Prince Eugène, Viceroy of Naples, Joseph II, Holy Roman Emperor, Leopold II, Holy Roman Emperor, Francis II, Holy Roman Emperor, Semyon Zorich, Catherine the Great, Alexander I of Russia, Stanisław August Poniatowski, Dositej Obradović) he met.
 He had valuable original notes on people, religions, manners, customs, trade, etc.
Karl Anselm, 4th Prince of Thurn and Taxis, full German name: "Karl Anselm Fürst von Thurn und Taxis" (2 June 1733, Frankfurt am Main, Free Imperial City of Frankfurt, Holy Roman Empire – 13 November 1805, Winzer bei Regensburg, Electorate of Bavaria, Holy Roman Empire) was the fourth Prince of Thurn and Taxis, Postmaster General of the Imperial Reichspost, and Head of the Princely House of Thurn and Taxis from 17 March 1773 until his death on 13 November 1805.
 Karl Anselm served as "Prinzipalkommissar" at the Perpetual Imperial Diet in Regensburg for Joseph II, Holy Roman Emperor and Francis II, Holy Roman Emperor from 1773 to 1797.
Frederick I (German: "Friedrich I" , Italian: "Federico I" ; 1122 – 10 June 1190), also known as Frederick Barbarossa (Italian: "Federico Barbarossa" ), was the Holy Roman Emperor from 1155 until his death.
 He was elected King of Germany at Frankfurt on 4 March 1152 and crowned in Aachen on 9 March 1152.
 He became King of Italy in 1155 and was crowned Roman Emperor by Pope Adrian IV on 18 June 1155.
 Two years later, the term "sacrum " ("holy") first appeared in a document in connection with his Empire.
 He was later formally crowned King of Burgundy, at Arles on 30 June 1178.
 He was named "Barbarossa " by the northern Italian cities which he attempted to rule: Barbarossa means "red beard" in Italian; in German, he was known as "Kaiser Rotbart ", which has the same meaning.
The monarchs of Prussia were members of the House of Hohenzollern who were the hereditary rulers of the former German state of Prussia from its founding in 1525 as the Duchy of Prussia.
 The Duchy had evolved out of the Teutonic Order, a Roman Catholic crusader state and theocracy located along the eastern coast of the Baltic Sea.
 The Teutonic Knights were under the leadership of a Grand Master, the last of whom, Albert, converted to Protestantism and secularized the lands, which then became the Duchy of Prussia.
 The Duchy was initially a vassal of the Kingdom of Poland, as a result of the terms of the Prussian Homage whereby Albert was granted the Duchy as part of the terms of peace following the Prussian War.
 When the main line of Prussian Hohenzollerns died out in 1618, the Duchy passed to a different branch of the family, who also reigned as Electors of Brandenburg in the Holy Roman Empire.
 While still nominally two different territories, Prussia under the suzerainty of Poland and Brandenburg under the suzerainty of the Holy Roman Empire, the two states are known together historiographically as Brandenburg-Prussia.
 Following the Second Northern War, a series of treaties freed the Duchy of Prussia from any vassalage to any other state, making it a fully sovereign Duchy in its own right.
 This complex situation (where the Hohenzollern ruler of the independent Duchy of Prussia was also a subject of the Holy Roman Emperor as Elector of Brandenburg) laid the eventual groundwork for the establishment of the Kingdom of Prussia in 1701.
 For diplomatic reasons, the rulers of the state were known as the King in Prussia from 1701 to 1772; largely because they still owed fealty to the Emperor as Electors of Brandenburg, the "King in Prussia" title (as opposed to "King of Prussia") avoided offending the Emperor.
 As the Prussian state grew through several wars and diplomatic moves throughout the 18th century, it became apparent that Prussia had become a Great Power that did not need to submit meekly to the Holy Roman Empire.
 By 1772, the pretense was dropped, and the style "King of Prussia" was adopted.
 Thus it remained until 1871, when in the aftermath of the Franco-Prussian War, the King of Prussia Wilhelm I was crowned German Emperor.
 From that point forward, though the Kingdom of Prussia retained its status as a constituent state of the German Empire, all remaining Kings of Prussia also served as German Emperor, and that title took precedence.
The German Emperor (German: Deutscher Kaiser) was the official title of the head of state and hereditary ruler of the German Empire.
 A specifically chosen term, it was used between the 18 January 1871 proclamation of King of Prussia and President of the North German Confederation Wilhelm I as ""Deutscher Kaiser"" and the official abdication of Wilhelm II on 28 November 1918.
 The Holy Roman Emperor is sometimes also called "German Emperor" when the historical context is clear, as derived from the Holy Roman Empire's official post-1512 title of "Holy Roman Empire of the German Nation."
The Concordat of Worms (Latin: "Concordatum Wormatiense" ), sometimes called the Pactum Calixtinum by papal historians, was an agreement between Pope Calixtus II and Holy Roman Emperor Henry V on September 23, 1122, near the city of Worms.
 It brought to an end the first phase of the power struggle between the Papacy and the Holy Roman Emperors and has been interpreted as containing within itself the germ of nation-based sovereignty that would one day be confirmed in the Treaty of Westphalia (1648).
 In part this was an unforeseen result of strategic maneuvering between the Church and the European sovereigns over political control within their domains.
 The King was recognised as having the right to invest bishops with secular authority ("by the lance") in the territories they governed, but not with sacred authority ("by ring and staff").
 The result was that bishops owed allegiance in worldly matters both to the pope and to the king, for they were obliged to affirm the right of the sovereign to call upon them for military support, under his oath of fealty.
 Previous Holy Roman Emperors had thought it their right, granted by God, to name Church officials within their territories (such as bishops) and to confirm the Papal election (and, at times of extraordinary urgency, actually name popes).
 In fact, the Emperors had been heavily relying on bishops for their secular administration, as they were not hereditary or quasi-hereditary nobility with family interests.
 A more immediate result of the Investiture struggle identified a proprietary right that adhered to sovereign territory, recognising the right of kings to income from the territory of a vacant diocese and a basis for justifiable taxation.
 These rights lay outside feudalism, which defined authority in a hierarchy of personal relations, with only a loose relation to territory.
 The pope emerged as a figure above and out of the direct control of the Holy Roman Emperor.
Holy Roman Empress or Empress of the Holy Roman Empire is the title given to the consort (wife) or regent of the Holy Roman Emperor.
 The elective dignity of Holy Roman Emperor was restricted to males only, therefore there was never a Holy Roman Empress regnant, though women such as Theophanu or Maria Theresa of Austria, who controlled the power of rule, served as de facto Empresses regnant.