Jamieson, Fausset and Brown on Joel 3:6

6. Grecians--literally, "Javanites," that is, the Ionians, a Greek colony on the coast of Asia Minor who were the first Greeks known to the Jews. The Greeks themselves, however, in their original descent came from Javan (Ge 10:2, 4). Probably the germ of Greek civilization in part came through the Jewish slaves imported into Greece from Phoenicia by traffickers. Eze 27:13 mentions Javan and Tyre as trading in the persons of men.

far from their border--far from Judea; so that the captive Jews were cut off from all hope of return.