scholiast
A scholar who writes commentary on the works of an author, especially one of the ancient commentators on classical authors.
[N]o pedantic quotations from Talmudists and scholiasts […] ever marred the effect of his grave and temperate discourses.
Where it comes from
From Late Latin scholiasta, from Byzantine Greek σχολιαστής (skholiastḗs), from σχολιάζειν (skholiázein), from Ancient Greek σχόλιον (skhólion).
Adapted from the Wiktionary entry scholiast (CC BY-SA 4.0).