Learn English – Where did the word “alphabet” come from

According to the OED, the term OK began its days as a humorous initialism “apparently derived from the initial letters of oll (or orl) korrect, jocular alteration of ‘all correct’ ”, when it was first seen almost 200 years ago in the United States, way back in 1839.

It seems that this sort of off-kilter formation was considered quite funny at the time: “an instance of a contemporary vogue for humorous abbreviations of this type” per the OED.

By 1840, this use was “greatly reinforced by association” with another identical initialism O.K., this one derived from the nickname Old Kinderhook adopted by Martin Van Buren during his 1835 electoral campaign for the U.S. presidency. The corresponding verb was soon null-derived¹ from this initialism around 1882.

The OED further notes (with bold emphasis added in this post for clarity) that:

Other suggestions, e.g. that O.K. represents an alleged Choctaw word oke ‘it is’ (actually the affirmative verbal suffix -okii ‘indeed, contrary to your supposition’), or French au quai, or Scottish English och aye, or that it derives from a word in the West African language Wolof via slaves in the southern States of America, all lack any form of acceptable documentation.

The OED further states that “Competing theories as to the origin of the expression have been in evidence almost since its first appearance”, and then provides several early completing theories in support of that assertion.

Footnotes

1. Null derivation, also known as zero derivation, is when a word is conscripted unchanged into use for a part of speech that’s different from the customary one. It has no derivational affix and so is said to be null derived, such as when we null-derive nouns from adjectives in The Good, the Bad, and The Ugly. A clearer example of this is the classic refrain that “verbing weirds language”, which features two instances of null-derivation: not only does it null-derive a new verb “verb” from its noun and then uses its verbal -ing inflection as a subject, it also null0derives a new verb “weird” from its adjectives and then uses the new verb’s third-person singular inflection.

An Ngram of the term shows its birth as a "stock phrase" only dates back to the 1960s, but the words are found in print a century earlier and the first examples of the phrase being used to mean motivating, inspiring, or enabling forces or factors go back to the 1930s. I'll give you one example of each.

I found creative juices in print back to this 1846 translation (p. 182, scroll down) of Kalevala, a Finnish epic poem that recounts a mythical story of the cursed birth of steel:

I don't think this reference is incidental. The same section of this poem, with the same translation, was reprinted several times in the writings of Lafcadio Hearn at the turn of the century and as late as 1922. While not the figurative use of the phrase we have today, I think there's a good chance its occurrence in his writings led to its familiarity and adaptation in the 1930s.

The first use of it I could find in print with its modern connotation was from this 1936 article in The Delineator:

[...] and played and replayed and recorded and wrote down their early songs. Their creative juices dried up. Only a few of the original players stuck by their guns, among them notably the men mentioned in this article. They continued, in honky-tonks, dives and dance halls, to play as they felt and feel as they played.

I wasn't able to get a more complete quote because of the limitations of Google's Snippet view, but it's clear the article is referring to the figurative creative juices of musicians.

One later 1930s reference of note is found in the intro to the 1939 screenplay of Margaret Mitchell's Gone with the Wind.