Ehwaz Analysis
Etymology and PIE origins
PGmc *Ehwaz from PIE *ekwaz -> OE Eoh (Horse), compare with N. H. G. Eh (Marriage). Cognate with Skt Asvah, Latin Equus, O. Celtic Equuns (-> Gaulish Epona)
Most of the words relate to horses, but it is worth noting that the New High German word Eh meaning marriage is related to the same term. This makes a fair bit of sense to anyone who has ever done much horseback riding (I relate horseback riding to dancing in terms of leading and following, and the types of trust that is required to be successful at it).
The Armanen tradition makes a great deal of the marriage relationship and they connect it closely to love magic. I certainly don't deny this aspect of the stave as it is grounded in the linguistic lore, but there are other aspects of the runestave as well that need to be considered. It is also noteworthy that the Mod. Eng. word Husband originally was primarily an agricultural term and that this survives in phrases like "animal husbandry" and "husbandry of the land." What is interesting is that while the term "Husband" was closely tied to cultivation and generation (i.e. he who plants the seed), the term "Eh" in German seems to be more closely tied to companionship.
The horse was extremely important to the Indo-European peoples, and it is likely that the combination of the domesticated horse and the spoked wheel were responsible for the successful expansion of the Indo-Europeans from the Tocharians in central China to the Celtiberians in what is now Spain and Portugal.
In the Middle Ages, the two main companions of a knight were his horse and his sword, and it is quite common to find knights talking to their horses and swords in Medieval heroic poems (I believe that both are found in the Song of Roland but I have not read it in a number of years, so I could be wrong). I strongly suspect that this concept of Horse as Companion is probably much older and either traces to the Gothic invasions or more likely to the most ancient Indo Europeans. (My case for this rests largely on the symbolic sexual intercorse involved with a sacrificed horse in the Vedic Asvamedha.)
Rune Poems
Ehwaz only exists in the OERP among the rune poems. It discusses this stave as a comfort to the restless (a constant companion for the traveller) and as a pride among the noble.
Myths and Kennings
Ships are called stallions of the sea in quite a number of Indo-European traditions (this kenning is found in Norse, Old English, and Greek poetry to name a few).
We have the stories of the horse being a work companion in the myth of the building of Asgard. Here the Etin's horse is distracted by Loki in the form of a mare so that he cannot finish the work in time. Loki later gives birth to Sleipnir (the one who slips, presumably a reference to agility rather than a lack of sure-footedness), Odhinn's horse. Loki's other children are closely related to death and distruction: Fafnir (the wolf who maims Tyr's hand, and will swallow Odhinn at the end of the world), Jormungond (the Serpent of the sea who will slay Thorr at the end of the world), and Hel herself, but here the only assication with death and destruction are due to Sleipnir's association with Odhinn.
Also Sigurd's horse, Grani is decended from Sleipnir, and it is on this horse that he rides through the wall of fire in the guise of Gunnar to trick Brynhild into marrying Gunnar. Note here we have the fact that he had (prior to drinking the draught of forgetfulness) promised to marry Brynhild, so here we see two aspects of companionship at work-- the mutual trust of Sigurd and Grani and the deception by which Sigurd tricks Brynhild, his former betrothed.
