Seoul

wiktionary

ref

From Korean 서울(Seoul, literally “capital city”), using a variant of Claude-Charles Dallet's French-based romanization of Korean, reinforced by the 1959 South Korean Ministry of Education romanization of Korean, which adopted Dallet's treatment of transcribing the Korean vowel ㅓ(/ʌ/) with the digraph "eo" and which was official until 1984.

Note that English Seoul predates the Revised Romanization romanization of Seoul. The two romanization systems simply produce identical forms.

etymonline

ref

Seoul

South Korean capital, from Korean soul, literally "capital." It was the national capital from 1392 until Japanese annexation in 1910.