etirabys:

Given names in Korean are almost always two syllables, with the first syllable usually being shared with your siblings and cousins (all the children of the same generation of a family, basically). I just grew up with this and didn’t think it was weird until I had cause to explain it to someone yesterday, at which point I stopped and wondered if I was making all of this up, it seemed so weird, how the heck do they coordinate that? Do the parents of the first kid of the new generation decide, or something? That doesn’t sound right. I looked it up, and it turns out that family lines keep a constant character array in a poem:

The sequence of generation is typically prescribed and kept in record by a generation poem (bāncì lián 班次聯 or pàizì gē 派字歌 in Chinese) specific to each lineage. While it may have a mnemonic function, these poems can vary in length from around a dozen characters to hundreds of characters. Each successive character becomes the generation name for successive generations.^[1] After the last character of the poem is reached, the poem is usually recycled though occasionally it may be extended.

Generation poems were usually composed by a committee of family elders whenever a new lineage was established through geographical emigration or social elevation. Thus families sharing a common generation poem are considered to also share a common ancestor and have originated from a common geographical location.

Which is mindblowingly cool, I think.