"I'm your huckleberry" usually conveyed the meaning of being the right person for a particular job. It can also mean, "I'm the person you're looking for." The phrase came into vogue in the late 1800s and early 1900s. The origin of the phrase is uncertain.
A common theory is that the phrase evolved from the earlier phrase "a huckleberry to a persimmon." Because a huckleberry is small and a persimmon is large, people used the phrase to describe something small in comparison with something larger. For example, "betting a huckleberry to a persimmon" meant placing a much smaller bet than someone who recently placed a large bet. Later, a huckleberry took on the meaning of a sidekick, or a partner lesser in stature or importance to his counterpart. Finally, by the late 19th century, slang dictionaries defined the phrase as "a man needed for a particular purpose."
Another theory is that the phrase came from Mark Twain's character of Huckleberry Finn. When "The Adventures of Tom Sawyer" was published, a huckleberry, in its sense of smallness, sometimes referred to someone inconsequential. Therefore, Twain admitted that the character's name reflected his lower position in society compared to Tom Sawyer. Huckleberry Finn's role as Sawyer's loyal companion may have contributed to the phrase's evolution. However, some observers argue that the phrase was already in use at the time of the book's publishing