"Cheonjamun", a Korean textbook of chinese characters, has its own form in representing the characters. For each character, that shows its Saegim (meaning) and Eum (sound) at the same time. Once a vocabulary to represent. Saegim of one character is settled, mostly it remains unchanged in every different edition throughout the times. However, in "Gwangju Cheonjamun" and "Seokbong Cheonjamun" written in the 16th century, despite their temporal adjacency, there are some number of different vocabularies fir the same character. The types of change of Saegims in "Seokbong Cheonjamun" into those in "Gwangju Cheonjamun" fall roughly under the following categories: 1) Saegim turned more generalized or more concrete when semantic scope of each character had been changed. 2) former Saegim was replaced by its synonym 3) parts of speech in Saegim were changed. From these changes, replacements between native Korean and sino-Korean etc. can be found. This paper will look into the aspects of those changes and deal with so called `rare Saegim vocabulary`. Generally, `rare Saegim vocabularies` are presumed to be fossilized form of vanished native Korean or affected by the influence of a dialect in Jeolla-province.