What are the earliest attested usages of the phrase "James the Great" (or "James the greater") in reference to "James son of Zebedee"?
The attestation will be in Greek or Latin. The earliest usage I know of is in The Perpetual Virginity of Blessed Mary/Against Helvidius by Jerome. Issued c.383 in Latin:
"Observe, Mary is the mother of James the Less and of Joses. And James is called the less to distinguish him from James the greater, who was the son of Zebedee..." https://www.newadvent.org/fathers/3007.htm