By the 4th century, Byeonhan had been replaced by the Gaya confederacy. Gaya traded extensively with the
Chinese commanderies in northern Korea and with Japan, but was absorbed by Silla in the 6th century. Much of our knowledge of Gaya comes from the
Samguk sagi, a history of the Korean
Three Kingdoms period, written in
Classical Chinese and compiled in 1145 from records of the kingdoms of
Silla,
Goguryeo and
Baekje that are no longer extant. Chapters 34, 35 and 36 survey the geography of the former kingdoms of Silla (including the former territory of Gaya), Goguryeo and Baekje respectively. They also cover the administrative re-organization after unification as
Later Silla in 668, including former place names and the standardized two-character
Sino-Korean names assigned under
King Gyeongdeok in the 8th century. Some of the places named in Chapter 34 are in the area of the former Gaya confederacy, but attempts to interpret them are controversial. The only word directly attributed to Gaya is found in an explanatory note in the same chapter, which reads: The Chinese character was used to write the
Silla word for 'ridge', which was ancestral to Middle Korean
twol 돌 'ridge', suggesting that the Gaya word for 'gate' may have been pronounced something like
twol. This looks similar to
Old Japanese to1 (modern Japanese , ), meaning 'door, gate'. ==References==