First attested in theWorin seokbo (月印釋譜 / 월인석보), 1459, asMiddle Korean설〯 (Yale:sěl).
The word설(seol,“Lunar New Year”) originally meant both "New Year" and "year of age". The two terms are connected; in Korea, one gains a new year of age at every New Year (so that all people born in the same year have the same age). In the eighteenth century, speakers created the new term살(sal,“year of age”) as a yang-vowel alternation of설(seol), and the original term came to mean only the New Year.설(seol) and살(sal) are one of a number of Korean noun pairs with yin-yang vowel alternation which were originally the same word.
In traditional East Asian age reckoning, a baby is one year old at birth and turns two years old onNew Year's Day. Thus everyone born in the same year is the same age: the current year subtracted by the year of birth, plus one.
