John Calvin Commentary Daniel 8:20-21

"The ram which thou sawest, that had the two horns, they are the kings of Media and Persia. And the rough he-goat is the king of Greece: and the great horn that is between his eyes is the first king." — Daniel 8:20-21 (ASV)

By the word “Javan” the Hebrews designate not only the Greeks but the Macedonians, and that entire tract which is divided by the Hellespont, from Asia Minor as far as Illyricum. Therefore the meaning is — the king of Greece.