Many cultures have the idea that names can carry a tremendous amount of power, and especially that they can grant access to a person's or an animal's and/or geological feature's inner-most being. That path of access could be threatening when held in the hands of someone with malevolent designs, so many cultures safeguard the "true" name, using a "circumlocution" (an alternative casual name) in everyday conversation.

The following is an excerpt from my Introduction to Folklore addressing this:

People place extensive cultural prohibitions on themselves regarding what can be said and done. In post-modern America, the shock value of violating traditional prohibitions has desensitized society and broken down many time-honored barriers. Pre-industrial societies strictly defined which things were allowed and which ones were forbidden. Anthropologists often use the Polynesian terms of noa (allowed) and tabu (forbidden) because the island people of the Pacific provide excellent examples of how the widest possible array of actions could come under complicated rules of prohibition. Indeed, the Polynesian example is so well-known that the word “taboo” has found its way into common English usage.

Taboos can apply to the entire community, to a group within the community, or they can be imposed (by oneself or by others) on individuals. Irish early-medieval epics, grounded firmly in folklore, contain the concept of the geasa, which was a taboo that someone magically placed on another. The degree of the magic was often unspecified, extremely weak, or even non-existent, but a person under a geasa was obligated to follow its restrictions.

Hawaiian society developed an extensive complex of taboos. Certain foods were restricted to the royal family or to other groups. Specific words and actions were prohibited for some and required of others. Taboos could even restrict who was allowed to look at a member of the royal family. Violations could be punished in the harshest ways since the well-being of the community at large was at stake.

Shared cultural taboos might include the idea that it is improper to point at stars. Specifically naming certain mountains, animals, supernatural beings, and other things could be prohibited, particularly in their presence. Various cultures have consequently provided a range of noa names for various things. Anthropologists also refer to these alternative means of address as circumlocutions. A noa name is used under circumstances when the actual name would be taboo. Northern European bakers avoided naming the fire, but instead spoke of the heat. Butchers would not refer to blood. They replaced that word with “sweat.”

The English word “bear” descends from the Proto-Germanic root *beron meaning “brown one.” This was apparently a way of avoiding the original word *rkto, from which was related to the Latin ursus. In this case, prehistoric speakers of ancestral English presumably avoided the actual name until it ceased to be remembered. Ethnographic evidence from the northern latitudes indicate that one should not name the bear in its presence (that is, in the forest) or when planning to hunt for a bear. Compare, for example, Russian medved, which means honey eater, and Swedish sotfot, meaning “sweet foot.” Both refer to the bear’s interest in honey. Native American Shoshoni politely discuss the bear as “our father’s sister.”

Words applied to the supernatural beings of nature provide what appear to be additional examples of circumlocution, which are particularly pertinent for a discussion of folklore. The English word “elf” descends from a root word that apparently described a shimmering, shiny appearance. It is related to the name Alps, the Swiss mountains, and the River Elbe in Germany. Because the term “elf” originally referred to a characteristic of the supernatural beings as opposed to what had been an actual, presumably-taboo name, it would be easy to assume that this term is a circumlocution. It is possible, however, that there never was a proper name for these supernatural beings, who were simply discussed in polite, descriptive ways. Eventually, however, people forgot the original meaning of the term “elf,” and as it became regarded as a proper name, various other circumlocutions including the “good neighbors” or the “fair folk” became alternatives safer than saying “elf.”

Similar circumlocutions are found elsewhere, Scandinavian elves are often called hulderfolk or simply huldre, meaning the “hidden folk” or the “hidden ones.” The Irish word for fairies, sidhe (hence, for example, banshee – woman fairy), was once a noa name that made reference to living in a mound. But again, there may have been no taboo, proper name that was being avoided. Centuries of use have made the term sidhe sacred, and it is now avoided. Instead the Irish may speak of the “wee folk” or the “beautiful ones.” Each culture can have a range of contrasting noa and taboo words, even if there are only linguistic remnants of this practice.

edit: to answer your specific questions: all anthropologists and folklorists can say is that these beliefs seem to be common property among many cultures. There is no evidence of diffusion of this idea unless we imagine some ancient tradition many tens of thousands of years old. While that is possible, it can only remain a matter of speculation and cannot be easily proven. In addition, these cultural traditions clearly do not draw from any literary source such as The Odyssey. Diffusion occurred from oral tradition to literature, not the other way around.

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