What is the origin of "steely eyed"?

Question

There was a question of the "grey eyed" epithet of Athena on Mythology recently, and one of the answers related to Athena's perceptiveness.

(The choice of "grey eyed" by translators is both poetic, and relates to a proposed connection between the Greek word of own and an adjective used for the color of the sea.)

What interests me here is the quality of perceptiveness, which enhances information gathering and analysis, leading to Athena's superior judgement and wisdom.

How is "grey eyed" related to "steely eyed" beyond mere color? What are early appearances of "steely eyed"?

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Note: I don't agree with the common definition of steely eyed, which seems to miss the point of the idiom. My understanding of steely eyed, based on context and usage, is related to realism, rationality, and canniness drawn from experience. Toughness/determination is merely the affect or appearance, and doesn't get to the root of the usage. That said, toughness and determination are traits also possessed by the armored, steely-eyed Athena. Where the common definition intersects with the deeper meaning is in regards to "mindset" (The mind is also the domain of Athena.) The determination connoted by being steely-eyed comes from a realistic assessment of a given situation, which is to say, analysis.

Part of what leads me to this conclusion is that, in this case, the adjective is applied very specifically to an organ of sense, which is to say perception. This is quite distinct from merely being determined as in having a "grim visage" or other idioms, and distinct even from "having a thick skin", which is also sensory.

To further this point, steel can be keen (have a keen edge) and it is notable that definitions of keen in include "sharp or penetrating", where sharp is also a term for mental acumen, and penetrating can be applied in the context of perception. (In Hermeticism, the sword is a symbol of intellect.) Even the use of keen for enthusiasm requires intellectual engagement.

Answer 1

According to my Google Books results, "steely eye" predates "steely-eyed":

For, after he had delivered the invitation, and made all the verbal statements he thought desirable, which Mr. Warrington received without interposing any remark or question, and even, when he had fairly concluded, said, as if waiting for something more, ' Yes ?' and ' Well, sir ?' so that Topperson repeated himself a good deal, while that searching, steely eye seemed to read him through and through[...]
_{The Monthly Christian Spectator, 1858}

The earliest real result for "steely-eyed" is from 1882, but it's a translation of another language:

And many a steely-eyed one hath received thy bright reflection fair.
_{Ottoman Poems: Translated Into English Verse in the Original Forms, with Introduction, Biographical Notices, and Notes}

The next result is from 1885:

Geraldine looked upon her husband and the steely-eyed old lady as her gaolers, and fancied she detected looks of intelligence between them.
_{A dog with a bad name, by Florence Warden, Volume 3}

"Steely-eyed" seems to parallel similar expressions that existed at the time such as "steely hearted" (which is significantly older). However, it's also worth noting that there are a number of results for "steely blue eyes", the earliest being in 1884:

"Yes, I certainly would, were I you," remarked Captain Grey, half closing his light and somewhat steely blue eyes.
_{Littell's Living Age, Volume 160}

And one for "steely-blue eyed" from 1882:

The people have all the Scandinavian characteristics, being fair-haired, blue-eyed, and tall in stature, in marked contrast with the dark-complexioned, small-sized, and black or steely-blue eyed Celts[...]
_{The Peoples of the World: Being a Popular Description of the Characteristics, Condition, and Customs of the Human Family, Volume 6}

Answer 2

It's possible that using "steely" as a figurative adjective in this sense was popularized by Shakespeare.

Yet these fixed evils sit so fit in him

That they take place when virtue's steely bones

Look bleak i'th' cold wind. Withal, full oft we see

• William Shakespeare, All's Well That Ends Well, 1604-5

However, as is often the case with word-innovations attributed to Shakespeare, OED provides attestations that antedate his writing.

O tough & stely hertes, o hertes more hard than flynte or other stone.

• John Fisher · This treatise concernynge the fruytfull saynges of Dauyd · 1st edition, 1508 (1 vol.).

OED seems to have dropped the ball (or lost interest) in "steely-eyed" or "steely eyes," attesting the combination in 1964. It does offer "steely blue eyes" in 1878, but no ocular variants as early as the 1858 finding by Laurel.

The black or steely-blue eyes of the Celts.

• Samuel Smiles · Robert Dick: Baker, of Thurso; geologist and botanist · 1878.