Eunuchs in the ancient world have become something of a major topic of interest for me over the past few years. The perception of eunuchs in various cultures throughout history has varied drastically, depending on the culture, the time period, and the kind of eunuch in question. I can only describe the perception of eunuchs in the ancient Mediterranean world, which is my area of historical specialization.

In general, in the ancient Mediterranean world, eunuchs were heavily socially marginalized. They were often of enslaved status and, because of their castration, they were commonly seen as no longer men, but rather lesser, inferior creatures. Eunuchs, women, and children were commonly seen as belonging to the same essential category and eunuchs were often seen as more similar to women than to non-castrated men. In the highly misogynistic ancient world, this made them seen as inferior and, in some cases, even outright disgusting and debased.

Eunuchs in the ancient Near East

In the ancient Near East, young men who were being sold into slavery were often forcibly castrated. Enslaved eunuchs were highly valued because they were incapable of fathering children and they were commonly thought to lack sexual desire. They were seen as ideal for serving in royal and wealthy households, because it was assumed that they would not have sexual relations with the wives and/or daughters of the king or wealthy person who owned them. (In reality, as we will see later, eunuchs do not always completely lack sexual desire and there are many attested stories of eunuchs enjoying sexual activities.)

In the Neo-Assyrian, Neo-Babylonian, and Achaemenid Empires, eunuchs commonly served as (among other things) custodians of the king's wives and children, royal bodyguards, and trusted messengers and ambassadors. The Greek word εὐνοῦχος (eunoûchos), from which the English word eunuch is derived, literally means "bed-keeper." As a result of their trusted positions and close proximity to the throne, certain eunuchs could become very powerful and influential within royal courts.

The Greek historian Herodotos of Halikarnassos (lived c. 484 – c. 425 BCE) records a famous story in his Histories 8.105-106 about a man named Hermotimos of Pedasa who he says was sold into slavery and forcibly castrated, but later went on to become the favorite eunuch of the Achaemenid king Xerxes I (ruled 486 – 465 BCE) and used his position of authority at the Achaemenid court to wreak poetically just vengeance against the very man who had castrated him many years earlier. Herodotos writes, as translated by A. D. Godley:

"Hermotimos, who came from Pedasa, had achieved a fuller vengeance for wrong done to him than had any man whom we know. When he had been taken captive by enemies and put up for sale, he was bought by one Panionios of Chios, a man who had set himself to earn a livelihood out of most wicked practices. He would procure beautiful boys and castrate and take them to Sardis and Ephesos where he sold them for a great price, for the barbarians value eunuchs more than perfect men, by reason of the full trust that they have in them. Now among the many whom Panionios had castrated was Hermotimos, who was not entirely unfortunate; he was brought from Sardis together with other gifts to the king, and as time went on, he stood higher in Xerxes' favor than any other eunuch."

"Now while the king was at Sardis and preparing to lead his Persian army against Athens, Hermotimos came for some business down to the part of Mysia which is inhabited by Chians and called Atarneus. There he found Panionios. Perceiving who he was, he held long and friendly converse with him, telling him that it was to him that he owed all this prosperity and promising that he would make him prosperous in return if he were to bring his household and dwell there. Panionios accepted his offer gladly, and brought his children and his wife."

"When Hermotimus had gotten the man and all his household into his power, he said to him: 'Tell me, you who have made a livelihood out of the wickedest trade on earth, what harm had I or any of my forefathers done to you or yours, that you made me to be no man, but a thing of nought? You no doubt thought that the gods would have no knowledge of your former practices, but their just law has brought you for your wicked deeds into my hands. Now you will be well content with the fullness of that justice which I will execute upon you.'"

"With these words of reproach, he brought Panionios' sons before him and compelled him to castrate all four of them—his own children; this Panionios was compelled to do. When he had done this, the sons were compelled to castrate their father in turn. This, then, was the way in which Panionios was overtaken by vengeance at the hands of Hermotimos."

Regardless of whether this specific story is historically true, it neatly illustrates the way some eunuchs could go from the slave market to relatively privileged positions within the royal court.

Nehemiah, a Jewish man who served as a cupbearer to the Achaemenid king Artaxerxes I (ruled 465 – 424 BCE) and later served as the Achaemenid governor of Judah, is possibly implied in the Book of Nehemiah 2:6 to have been a eunuch, since he is described as standing in the queen's presence.

The Septuagint, the translation of the writings of the Hebrew Bible into Koine Greek made in the third and second centuries BCE, explicitly describes Nehemiah as a eunuch. Whether he actually was a eunuch historically is an open question, but it certainly would not have been unusual for someone in his position to have been a eunuch.

The majority of enslaved eunuchs probably never attained this kind of privilege, but it was possible for a lucky few.

(This answer is continued in the comment below.)