Seeking etymological explanation of card game Euchre based on its spelling

The origin of the game, euchre, must be seen as distinct from the origin of its name, 'euchre'. The game may well have originated in Germany; its name, elsewhere.

For instance, OED observes:

Etymology: Of uncertain etymology. As BOWER n.⁸, one of the terms used in this game, is of German origin, it has often been supposed that the word euchre is also from German, but no probable source has been found in that language. Can it be < Spanish yuca, in the phrase ser yuca, given by Caballero as an American expression for 'to be cock of the walk, to get the best in anything' (ser el gallito en alguna cosa, sobresalir en algo)?

[Bold emphasis mine.]

Evan Morris, in a December 1999 "The Word Detective" column, adds the levity of his inestimable opinion. In contrast to OED's earliest attestation in 1841 (an attestation added post-1989; the earliest attestation given in OED's 1989 edition was 1846), Morris dates the word's appearance to around 1848. He considers and discards an origin in 'Eucharist', then states

All of which leads us to the one even remotely plausible theory about "euchre" I've been able to root out, which is that "euchre" comes from the Spanish phrase "ser yuca," meaning "to be the best" or "to win." This origin would certainly make sense given the highly competitive nature of the game, and would also fit in with the slang use of "euchre" as a verb meaning "to win decisively."

I'm with Evan and OED on the name of the game coming from the distilled Spanish idiom, and have little to add in support other than that the earliest attestations I can find, from the popular press, appear as the variant 'eucre' around 1834 in southern US newspapers.

An earlier attestation of the word, probably an Americanized (and so r-colored) representation of a Cuban Spanish pronunciation of 'yuca', is this from an 1829 publication:

After breakfast, in looking round the place, we perceived seventy or eighty bushels of euchre, just dug...it is a species of cassavi, or cassada.

Letters Written in the Interior of Cuba, Abiel Abbot, 1829.

The first spelling of Euchre was "eucre" early 1800s (pre-1800) The game of eucre came about (my theory) by Alsatians who were embedded with Hessian Soldiers. The Alsatians taught their German counterparts the game. Many Hessian prisoners were held in Eastern Pa, MD and VA prison camps and let out to work locally. Some married into German families.

Eucre continued to be spelled this way well into early 1900s. The first time documented that the "h" was added was mid-1840s, Hoyle book Anners 1845. There was a big push, mainly by the British authors of various Hoyle Books (who authored most of the Hoyles until 1860s) to spell words one way.

It is documented by Fischers that the game of Jucker-spiel had the word "bauers" and the word "marsch" (meaning march or sweep). Obviously, our game of Euchre came from this game of Jucker, even though no one as produced the rules of this Alsatian game. And I think (my theory) for obvious reason that the bauer, meaning Peasant, was elevated in the game Jucker spiel. It was hit on the French Royalty, King Louis VI, social unrest leading later to the French Revolution. The feudal peasants rising with elevated power over Royalty. A forecast of social unrest and what was to come later. Of course popular for our American Revolution and those Alsatians where where French but with a German culture. Strasbourg, Alsace was always a seat of progress with lots of freedom at the University there. The country side were lands of feudal peasants that had German Princes that ruled with feudal rights.

So as the author or printer, inventor of this game, your would not want your identity to be known. Thus the game was not published.

As to the word "joker", it did NOT come from the word Jucker. Juckerspiel was not found as the parent game of Euchre until 1990 by David Parlett. You cannot find a source for the word Jucker being related to Euchre before his book, The Oxford Guide to Card Games. And the parent game of Jucker is the French Ruff or Triomphe.