'The debating club formed among these young friends at this era of their studies was called The Literary Society; and is not to be confounded with the more celebrated Speculative Society, which Scott did not join for two years later. At The Literary he spoke frequently, and very amusingly and sensibly, but was not at all numbered among the most brilliant members. He had a world of knowledge to produce; but he had not acquired the art of arranging it to the best advantage in a continued address; nor, indeed, did he ever, I think, except under the influence of strong personal feeling, even when years and fame had given him full confidence in himself, exhibit upon any occasion the powers of oral eloquence. His antiquarian information, however, supplied many an interesting feature in these evenings of discussion. He had already dabbled in Anglo-Saxon and the Norse Sagas: in his Essay on Imitations of Popular Poetry, he alludes to these studies as having facilitated his acquisition of German:—But he was deep especially in Fordun and Wyntoun, and all the Scotch chronicles; and his friends rewarded him by the honorable title of Duns Scotus.'
From John Gibson Lockhart's "Memoirs of the Life of Sir Walter Scott". The "Subtle Doctor", John Duns the Scot, died on November 8, 1308. Like Fordun and Wyntoun, Duns was a man of the cloth, though of the Catholic faith. He was ordained a Franciscan in 1291, and had a significant influence on Middle Age thought. The term "Scotism" applies to the school of philosophical and theological thought that Scotus developed. For more, see: http://plato.stanford.edu/entries/duns-scotus/
According to Lockhart, the Duns Scotus nickname stuck with Walter Scott for many years.