Short answers, pulled from the story.
The concept of a Dark Age was first introduced by the Tuscan scholar Petrarch in the 1330s, who used it to describe the post-Roman centuries as inferior to classical antiquity. The specific Latin phrase saeculum obscurum was coined by Cardinal Caesar Baronius in 1602, applied to the period from 888 to 1046.
Cardinal Caesar Baronius used the term to describe a lack of written records, not cultural or intellectual backwardness. He pointed to a sharp drop in Latin literary output in the 10th century, where only around 8 volumes of text survive compared to roughly 34 from the 9th century.
Most modern historians avoid the term because of its negative connotations, finding it misleading and inaccurate. Increased archaeological, historical, and literary scholarship since the 19th and 20th centuries has shown that the period was far more sophisticated than the label implies. In 2020, scholars John Blair, Stephen Rippon, and Christopher Smart noted that material culture from the 5th to 10th centuries demonstrates a high degree of sophistication.
Enlightenment writers including Voltaire, Kant, Hume, Jefferson, and Rousseau used the term to attack the Middle Ages as a period of religious domination opposed to reason. Edward Gibbon expressed contempt for what he called the rubbish of the Dark Ages in The History of the Decline and Fall of the Roman Empire.
In modern usage, 'Dark Ages' most commonly signals general backwardness or a lack of technological sophistication, with little or no reference to the actual medieval period. Howard Williams of Chester University noted in a 2021 lecture that the term is rife in newspaper articles and media debates, and Andrew B. R. Elliott's 2017 research found it is often used unconsciously as a trope criticizing lack of progress.
The Romantics of the late 18th and early 19th centuries reversed the Enlightenment's condemnation and idealized the Middle Ages as an Age of Faith and a Golden Age of chivalry. Figures like Horace Walpole helped launch the Gothic Revival in the arts, transforming 'Gothic' from an insult into a term of romantic admiration.