(text from churchofjesuschrist.org)
"The Aramaic word Rabboni, used by Mary to address the resurrected Savior, is used only twice in the New Testament. In John 20:16, the King James translators retained the Aramaic word and John’s translation for his readers, which is “Master.” In Mark 10:51, the word is translated as “Lord.” The title Rabbi was used for respected teachers among first-century Jews. Rabboni, a more lofty form of the title Rabbi, was a title that was rarely used and was usually reserved for highly esteemed teachers who had both divine knowledge and authority to teach others."
