I'll be your huckleberry

Where did this come from what does it mean? It was used in a movie.

From many undocumented guesses, conjectures and speculations!

The phrase is on many top ten lists of favorite quotes from Hollywood films:
"I'll be your huckleberry": Doc Holliday to Wyatt Earp in Tombstone. It was the WAY he said it. Great flick!!!

Anyway,
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".