I know that Byzantine is a relatively modern term used retrospectively by some historians to refer to the Eastern Roman Empire in the Middle Ages and that they generally called themselves some form of Roman (like Rhomaioi in Greek, which became the main language). And I know the eastern cultures like Turks and Arabs called them something based on that, like Rum. My question is what other European countries referred to them as over time?
Like for example, what would the Venetians (who had an uneasy often antagonistic relationship with them) during the Crusades have called them? Would they really have still called them "Romans" at this point? I feel like by that time, after the Schism, they lost legitimacy in that regard in the eyes of the West. Or what about other Italians, particularly from the area of Rome itself, and the Papal States? Would they have just called them the Greeks by this time? Same for the Germans of the "Holy Roman Empire", what would they have called the Byzantines? Or the Franks/French? Russians and other Slavs?
I assume it also changed over time... if you ask about this for 500 AD vs 1400 AD it would probably be pretty different.
u/AksiBashi recently wrote about when the term Byzantine empire was introduced
And, if I may, an older answer from me: What did the other people's of Europe call the Byzantine Empire? Did it differ depending on who you asked and were there any changes as the empire dwindled?
So the short answer is that "Byzantium" was also used in the Middle Ages sometimes, if someone wanted to sound archaic. The Byzantines themselves usually called it the Roman Empire, since that's what it was. That's what their eastern neighbours (Arabs, Persians, Turks, etc) called it too, since as far as they were concerned the Roman Empire had always been there.
In the former western empire in western Europe, they tended to call it the Empire/Kingdom of Constantinople, or the Empire/Kingdom of the Greeks.
The following post primarily only covers Old Norse-Icelandic texts, that is my narrow specialty.
In Old Norse-Icelandic literature, Byzantine Emperor is generally called just as en emperor or as "a king of the Greeks". To give an example, Emperor Alexios I Komnenos (d. 1118) is mentioned as "King Alexíus of the Greeks (Alexíus Grikkjakonungr) in the Book of the Icelanders (Íslendingabók), Chapter 10 (ÍF I: 25) (customarily dated prior to 1133) among obituary notices of different European rulers, and also as "Emperor Kirjalax (Alexios) (Keisar Kirjalax)" in Morkinskinna (customarily dated to about 1220), Chaps. 65 and 67 (ÍF XXIV: 86, 95). The latter text also mentions "Emperor Manuel (Keisari Manúli)" (Manuel I Komnenos, d. 1180), though erroneously identified him as son, not grandson of Kirjalax-Alexios (ÍF XXIV: 86). These two terms (King - Emperor) are employed almost interchangeably, I suppose.
Byzantine Empire is also often called as "the Greece land (Grikkland) (ÍF XXIV: 86), and its people, the Greeks are usually called Grikkir (plural form) in Old Norse.
Virtually all of these Old Norse texts are recorded onto parchments after the alleged Schism, and a few runic inscription texts from 11th century (now) Sweden also mentions "in Greece (í Grikkjum) or "in the land of the Greeks (á Grikklandi)", as such:
According to Sverrir Jakobsson, the alleged Eastern-Western Schism did apparently not affect the fame of Byzantine Emperor in Scandinavian/ Old Norse world (Sverrir Jakobsson 2008). Thus, different naming conventions of Romans-Greeks seemed not to have mattered little in medieval Scandinavia.
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On the other hand, primarily texts from medieval Germany might have chosen Emperor/ King depending more on the context or their characters.
To give an example, Abbot Arnold of Lübeck (d. around 1210?) calls Emperor Isaakios II Angelos (d. 12204)as "King of Constantonople (rex Constantonopolitanus)" in his Chronicle of the Slavs, IV-9 (linked to the original Latin edition in MGH SSrG) (MGH SSrG 14: 132), describing Frederick Barbarossa's pilgrimage to the Holy Land.
In the document of more formal character, however, the "emperor", though "of the Greeks", also seem to be preferred, as illustrated in the letter of Emperor Conrad III of HRE (d. 1152) to Emperor John II of the Byzantine Empire (d. 1143), cited in Otto of Freising's Deeds of Frederick Barbarossa (I-25):
"Conrad, by the grace of God august emperor of the Romans, to John, by the same grace emperor at Constantinople (Constantinopolitanus imperator), sends greeting and brotherly love. As our ancestors, namely, the emperors of the Romans, established friendship, honor, and glory with your predecessors, namely, the realm and the people of the Greeks (regnum et populum Grecorum), so do I established it, and as they preserved it even so will I preserve it. There is no race, kingdom, or people that knows not that your New Rome (nova Roma) is called and shall always be the daughter of the Roman republic......(The translation is taken from: [Mierow trans. 2004 (1953): 54), and the original text in Latin is found in MGH SSrG 46: 37f.)."
References:
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(Edited): adds annotations of the year of death for some persons mentioned.
