King Arachnophobius was the ruler of Attica. He was succeeded one after the other by his son King Agoraphobius, grandson King Xenophobius, great-grandson King Oeneus and finally great-great-grandson King Orestes Quoting his name was part of the coronation ceremony that Iolaus went through when he was taking the place of King Orestes.
As with most instances of ancient Greek in the Xenaverse, the sign bearing Arachnophobius's name is actually gibberish that doesn't use the Greek alphabet.