언니

Etymology
ko. The word is attested for the first time only in dictionaries of colloquial Korean published by Europeans in the 1890s, suggesting that it was a very recent neologism at that point. These dictionaries define the word as referring to any elder sibling of the same gender, instead of the female-exclusive word it is now. A number of etymologies attempt to connect the word to fifteenth-century Middle Korean morphemes, but these are clearly impossible given that none of these morphemes were productive by the late nineteenth century. A connection to Japanese is tempting but unlikely, given that there were few linguistic contacts between colloquial Korean and Japanese until the 1900s.

Perhaps the most reasonable hypothesis is the one given by Ito (2020), that it originated from an intentionally childish pronunciation of.

Noun

 * 1) older sister of a female
 * 2)  somewhat older female
 * 3)  elder brother of a male
 * 4)  unnie
 * 1)  elder brother of a male
 * 2)  unnie
 * 1)  elder brother of a male
 * 2)  unnie

Usage notes
This term is used as a de facto second-person pronoun by women to address both older sisters and unrelated women of somewhat older age. This is because Korean does not permit the use of true second-person pronouns towards a social superior. See 너 for more.