Where did the quotation 'I am your huckleberry' come from?

The phrase has ties to Arthurian lore. A Knight, coming to the service of a damsel would lower his lance and receive a huckleberry garland from the lady ( or kingdom) he would be defending. Therefore, "I am your huckleberry" may well have been spoken to the Earps and the statement's meaning may be "I am your champion".

The "Random House Historical Dictionary of American Slang, H-O" by J.E. Lighter (Random House, New York, 1997) lists several meanings: 1. minuscule amount. 2. a fellow; character; boy. "one's huckleberry," the very person for the job. 3. bad treatment. "the huckleberry" is similar to "the raspberry." 4. a foolish, inept or inconsequential fellow.

Another huckleberry phrase: "above one's huckleberry" -- beyond one's abilities. And "huckleberry train," one that stops at every station.

In the movie "Tombstone", Doc Holliday (played by Val Kilmer) spoke this phrase to Johnny Ringo on two occasions, (never to the Earps). Ringo was looking for a gunfight both times. In that usage, the meaning was from definition 2 of the Random House Dictionary of American Slang, meaning "I'm the man for the job".