I know the term "Byzantine" wasn't really introduced until the 19th century as a way for scholars to differentiate the empire during its medieval period and late antiquity, but from what I've read, the citizens of the "Byzantine" empire never referred to themselves as "Byzantine", and in fact never even referred to themselves as "Eastern Romans". They called themselves the Roman Empire and the people referred to themselves as Romans. Did this continue until the 1400s when Constantinople fell to the Ottomans?
This is not the answer. It's just to correct a misconception.
I know the term "Byzantine" wasn't really introduced until the 19th century as a way for scholars to differentiate the empire during its medieval period and late antiquity, but from what I've read, the citizens of the "Byzantine" empire never referred to themselves as "Byzantine", and in fact never even referred to themselves as "Eastern Romans".
Please see this thread. The term Byzantine was indeed used from time to time by people of the Empire to refer to themselves. Courtesy of /u/Ambarenya.