Heracles means "fame of Hera." Why he would be given that name, when Hera hates him in the myths, is an open question, but the name itself isn't confusing in the Greek. Hercules is the version in Latin -- it's a mispronunciation of the Greek name essentially... The relationship between "heros" and "Hera" is more complicated. They're both really old words, so any relationship between the two of them may relate to meanings that they no longer had in historical times. I'm reluctant to connect them to Egypt, as they both have pretty unique meanings tied to Greek culture.What Dave is describing there exactly is Osiris, as reinterpreted by the Greeks. What seems abundantly clear to me is that heros is indeed derived from Horus, since the Hellenes saw Osiris and Horus as the same personage- he and his father were one. And this has precedence in the Egyptian mysteries- In life the pharoahs were named as Horus and in death they became Osiris. The Greeks would later conflate the two, which is why Osiris is often misidentified as a Sun God today. This is most probably where heros came to be used to describe characters that fill the archetypal role of Osiris.
At any rate, defining "heros" as protector/defender is a bit of a mistranslation. A heros is a guy who in the past did amazing things but then got killed in a really humiliating way, so that his spirit will come back and curse the living, unless they make offerings to him. If they do make offerings to him, he'll make the crops grow, and keep the city from being attacked (crops and war are pretty closely linked for the Greeks).
"In the context of naming the king, the combination of the two aspects of Horus expresses the belief that the king exhibits the power of Horus the sun-god as well as the idea that he has received the kingship from his father Osiris. While young Horus represents the king on earth, Osiris stands for the dead king, the father and predecessor; both taken together describe the transition of power. The genealogical series of the names of the dynastic priesthood serves precisely the same function."
Quoted from Images and Ideologies: Self-definition in the Hellenistic World
Dave writes: The ambivalence of these figures is reflected in the rituals, which are similar to offerings given to the dead, and like the dead, their shrines are put at the edge of town, where they can do the least damage to the city, and the greatest damage to anyone coming to town to do bad things.
Even more instructive, however, is another representation of the same event in a chamber dedicated to Osiris in the great temple of Isis at Philae. Here we see the dead body of Osiris with stalks of corn springing from it, while a priest waters the stalks from a pitcher which he holds in his hand. The accompanying inscription sets forth that “this is the form of him whom one may not name, Osiris of the mysteries, who springs from the returning waters.” Taken together, the picture and the words seem to leave no doubt that Osiris was here conceived and represented as a personification of the corn which springs from the fields after they have been fertilised by the inundation. This, according to the inscription, was the kernel of the mysteries, the innermost secret revealed to the initiated. So in the rites of Demeter at Eleusis a reaped ear of corn was exhibited to the worshippers as the central mystery of their religion. We can now fully understand why at the great festival of sowing in the month of Khoiak the priests used to bury effigies of Osiris made of earth and corn. When these effigies were taken up again at the end of a year or of a shorter interval, the corn would be found to have sprouted from the body of Osiris, and this sprouting of the grain would be hailed as an omen, or rather as the cause, of the growth of the crops. The corn-god produced the corn from himself: he gave his own body to feed the people: he died that they might live.
And from the death and resurrection of their great god the Egyptians drew not only their support and sustenance in this life, but also their hope of a life eternal beyond the grave. This hope is indicated in the clearest manner by the very remarkable effigies of Osiris which have come to light in Egyptian cemeteries. Thus in the Valley of the Kings at Thebes there was found the tomb of a royal fan-bearer who lived about 1500 B.C. Among the rich contents of the tomb there was a bier on which rested a mattress of reeds covered with three layers of linen. On the upper side of the linen was painted a life-size figure of Osiris; and the interior of the figure, which was waterproof, contained a mixture of vegetable mould, barley, and a sticky fluid. The barley had sprouted and sent out shoots two or three inches long. Again, in the cemetery at Cynopolis “were numerous burials of Osiris figures. These were made of grain wrapped up in cloth and roughly shaped like an Osiris, and placed inside a bricked-up recess at the side of the tomb, sometimes in small pottery coffins, sometimes in wooden coffins in the form of a hawkmummy, sometimes without any coffins at all.” These corn-stuffed figures were bandaged like mummies with patches of gilding here and there, as if in imitation of the golden mould in which the similar figures of Osiris were cast at the festival of sowing. Again, effigies of Osiris, with faces of green wax and their interior full of grain, were found buried near the necropolis of Thebes.
- James Frazer, The Golden Bough
But since Hercules seems to want our attention lately, let's address Osiris/Horus' link to Hercules.
To take the Heracles connection in a different direction, I once heard a pretty plausible paper delivered arguing that some of the miracle stories about Jesus were originally stories about Hercules. The story I remember the most about was the one where Jesus drives the demon "Legion" into the herd of swine, which then run off a cliff and fall in the sea. Apparently there are no cliffs overlooking any of the seas in the holy land. However, by tracing connections between names, this scholar pointed to a place in Spain where the geography makes more sense, and where there was a temple to Hercules.
Well, yet again, we see another version of the swine story with Osiris. He sat at the judgement seat in the Afterlife and condemned the wicked to Hell in the form of a pig.
It's too bad the ancient mythologers didn't have a continuity cop. But a lot of scholars will tell you that Christianity itself was essentially the Roman hierarchy's version of Crisis On Infinite Earths- an imperial intervention to make sense of the competing belief systems- Paganism, the Mysteries, Judaism, Gnosticism, the various proto-Christian cults- so that the Empire could be united under a single faith. In this light, Constantine could be seen to be completing what Aurelian started. Scholars such as Ehrman believe that Constantine thought the god of the Bible was Sol, since the emperor continued to mint coins and build shrines to the sun god long after his supposed conversion.