Why is 洛 associated with Kyoto / the capital?

Question

I recently found out that the kanji 洛 is associated with Kyoto / the capital.

Here are some example words showing this association:

洛内【らくない】 : "in Kyoto or the capital"

洛外【らくがい】 : "outside Kyoto or the capital"

洛南【らくなん】 : "southern part of Kyoto​ / south of the capital"

I figured it must be from the time when Kyoto was Japan's capital, but I've been unable to find where the relation between 洛 and "capital" comes from.

Could it be similar to how, for example, 米 is associated to America, and 亜 with Asia? Maybe 洛 was used to write "capital" or "Kyoto" at some point?

Answer 1

It was because we Japanese borrowed many words from Chinese.

For example、洛陽｛らくよう｝ is the capital of 魏（English) in Three Kingdom Age.

Here Wiki says,

京都は、古く詩文において中国王朝の都に因み、洛陽、長安などと呼ばれた。一説に、平安京を東西に分割し、西側（右京）を「長安」、東側（左京）を「洛陽」と呼んだという[6]。ところが、右京すなわち「長安」側は湿地帯が多かったことなどから程なく廃れ、市街地は実質的に左京すなわち「洛陽」だけとなった。このため、「洛陽」とはすなわち京都を指す言葉になり、その一字を採って「洛」だけでも京都を意味することになったとされる[7]。

Kyoto was in old times called 洛陽 or 長安｛ちょうあん｝, appropriating the words of Chinese Empire's ( capitals ). A theory holds Kyoto was once divided into to 2 sides, East and West, respectively the West、右京｛うきょう｝ was called 長安、the East, 左京｛さきょう｝, was called 洛陽。Whereas, 右京 has lots of swampy lands, so that eventually the street style remained only in ( the East ), 左京、＝ 洛陽。 Therefore the word 洛陽 came to denote the center of Japan, and just using 洛 of 洛陽 became to denote the capital.

The famous another example is that 豊臣秀吉｛とよとみひでよし｝ was later called 太閤｛たいこう｝、which is the after name equivalent with Chinese one after he resigned the old Japanese political ranking 関白.

Answer 2

The use of 洛 comes from another way of referring to the eastern part of greater Kyoto area, namely 洛陽{らくよう｝.

洛陽: 平安京の左京（平安京の東半部）の称。右京を長安と称するのに対する。また、京都の異称。 // Rakuyou: The eastern half of the capitol of Japan during the Heian period. A way of differentiating from the western part (長安）.

Kyoto was modeled after the cities of Chinese cities of Chang'an (長安) to the west and Luoyang (洛陽) to the east.

As the eastern part was more central as far as administration, entertainment, etc., 洛陽 came to refer to Kyoto in general, or the main part of it at least.

The origin of the first character of the name of the Chinese city 洛陽 is from the the Luo (洛水）river to the south: 洛陽の南には洛水が流れており、これが地名の由来となっている.

大内裏｛だいだいり｝, the 'Greater Palace', in the center of 洛陽 was the dividing line between 洛西、洛東、洛北、etc. While no real landmarks really presently exist in the location of the former palace, the naming conventions were retained.

Some background here.　Also here.