What follows below is in no ways meant to be an exhaustive study, but just s short background overview.
The famous Helm of Awe has its origins in the tale of Fafnismal It is an item which brought fear to men and was amongst the treasures of the dragon. The dragon Fafnir, all powerful and the bringer of much destruction, and havoc, attributes much of his apparent invincibility to his use of the Helm of Awe.
When Sigurth slays Fafnismal the dragon offers Sigurth much irrelevamt advice as it lies dying, and a whole saga unfolds of back and forth discussion.
In the saga Fafnir tells Sigurth:
“I wore a terror-helmet against all men so long as I sat on my treasure. I thought I alone was braver than everyone: not many came to meet me.”
Sigurth said: “That terror-helmet will not save anyone when angry men come together to fight. When a real battle starts, you’ll always find that there is no bravest man.”
Much more happens in this tale. Like roasting and eating the heart of the dragon, drinking its blood amd more gore if you like a good battle tale. Oh and he speaks to some wagtails too.
But eventually Sigurth followed Fafnir’s tracks to his lair, and found the iron doors and gates open. All the pillars were also made of iron, and they were dug deep into the earth. Sigurth found a great quantity of gold there, and he filled two chests with it. He took the terror-helmet and a golden suit of armor, and the sword Hrotti and many other precious treasures, and he loaded them onto his horse Grani. But even with that burden, the horse would not start till Sigurth had mounted up on his back.
The actual visualisation of the symbol came much later, and was not very fixed in design. Many forms of what we now know as the Helm of Awe exist in a number of Manuacripts and Grimoires. Some with four arms others with eight. For example the seventeenth-century Icelandic grimoire, Galdrabók has a helm in figure 41. This one includes a drawing of the Helm of Awe with only four arms and without the sets of lines that run perpendicular to the arms. The more utilised form has eight legs and three sets of lines running perpendicular on each leg.
The Helm mentioned in the saga is most likely a sphere shaped object of energy and magickal origins. A sort of energy ball shaped item.The graphical representation however is a strong symbol with its origins in the runes. Algiz / Elhauz forms the arms. Algiz has a strong protective property and hence is a good use in this case. It could also potentially contain Isa in its form.
All in all the helm has a long history in its various forms, and is truly a tool in every Mage's tool kit.
Saga text Ref and extracts from Dr Jackson Crawford' translation of the Poetic Eddas.