Eumaeus is Odysseus' swineherd. When Odysseus finally ends his long journey upon returning from the island of the Phaiakians (or Phaeacians) he and Athena decide that it would be best if Odysseus went disguised as a beggar into his own palace. The fisrt encounter he has with a member of his household is with Eumaeus. During Odysseus' twenty-year absence , his son, Telemachus has grown from a boy into a man and has essentially adopted Eumaeus as a father. Though he is initally introduced as a swineherd we learn that his history is much more complex than that.
In fact, Eumaeus claims to have been the son of the king Ctesius, from the island of Syra. He was kidnapped by the Phoenecians and eventually brought to Ithaka and sold. Since then he has been relegated to the pigs by Penelope and has lived out his life as a faithful servant of the household, even during Odysseus' brief jaunt around the nether regions. This faithfulness is proven when, just before he's about to kill the suitors, Odysseus asks Eumaeus the swineherd and Philoetius the stockman if - hypotetically (since they have not yet seen through the disguise) - they would help Odysseus in killing the suitors if he were to return. Both servants prove faithful and eventually give Odysseus a helping hand in the slaughter of the suitors.
Lastly, it is interesting to note that Eumaeus is the only character in the poem who is addressed directly by the narrator. On multiple occasions the poem reads, "To this you answered, O swineherd Eumaeus," and then continues with the quotation. This suggests that Eumaeus is much more than a simple narrative device for the transition between "Odyssey" and "Homecoming," but this analysis is better suited to a critical essay on the poem.
(E2 DICTIONARY OF CLASSICAL MYTHOLOGY)
Table of Sources:
-Homer,Od. Books XIV-XX