Vovin and Unger suggest that it was the original form of Koreanic, which subsequently replaced Japonic languages in the south of the peninsula.

Chinese histories provide the only contemporaneous descriptions of peoples of the Korean peninsula and eastern Manchuria in the early centuries of the common era.

[9] To the south of the Chinese Lelang Commandery lay the Samhan ('three Han'), Mahan, Byeonhan and Jinhan, who the Records of the Three Kingdoms described in quite different terms from Buyeo and Goguryeo.

[13] Based on this text, Lee Ki-Moon divided the languages spoken on the Korean peninsula at that time into Puyŏ and Han groups.

Chapter 94 of the History of the Northern Dynasties (compiled in 659) states that the language of the Mohe in the same area was different from that of Goguryeo.

[15] The most widely cited evidence for Goguryeo is chapter 37 of the Samguk sagi, a history of the Three Kingdoms period written in Classical Chinese and compiled in 1145 from earlier records that are no longer extant.

[16] This chapter surveys the part of Goguryeo annexed by Silla, with entries like 七重縣一云難隱別The phrase 一云 'one calls' separates two alternative names for a place.

[19] It is generally agreed that these glosses demonstrate that Japonic languages were once spoken in part of the Korean peninsula, but there is no consensus on the identity of the speakers.

[30] Beckwith's linguistic analysis has been criticized for the ad hoc nature of his Chinese reconstructions, for his handling of Japonic material and for hasty rejection of possible cognates in other languages.

[42][43] Beckwith identified a dozen names of places and people in Chinese histories that he argued were Goguryeo words.