Origin of katakana ン (カタカナの「ン」の字源)

Question

Looking on various pages, the origin of ン seems to be very confused. Most lists either don't include ン, or list one theory. So far I've found the following options:

• 一
• 爾
• 无
• 尓
• 二
• 冫

Wikipedia also mentions

「ン」については漢字でなく撥音を表す記号（Ｖ）の変形とする説もある。
For ン there is also the theory of it not being derived from kanji, but rather being a variation of the notation "レ" representing the sound [ɴ].

Is "we just don't know" all there is to say about the origin of ン?

Answer 1

I took a look at the book OP mentioned and following is a super-simplified summary of how "ン" was invented, as described in the book. I'm no historian nor linguist, so I can't guarantee this is true.

• There was no kanji for "ん／ン" at all in Man’yōgana (万葉仮名). This is partly because, in those days, the Chinese writing system also had no simple character for the [n/m/ŋ] sound. Actually no one in East Asia knew how to write this sound using only one letter.

• In the early 9th century, Buddhist monks in Nara developed katakana, but there was no "ン" at first. This was natural because there was no kanji for "ン" in 万葉仮名 from which they extracted katakana.

• Instead, they developed several ways to express [n/m/ŋ] sounds in Buddhist scriptures. They mainly borrowed other existing katakanas. For example, "イ or ニ" for [n] (恨 = コニ), "ム" for [m] ([厭]{iεm} = エム), "イ" for [ŋ] ([痛]{t'nŋ} = ツイ).

• One way of writing [n] sound was "レ", which is seen in 地蔵十輪経【じぞうじゅうりんきょう】 written in 883. 鮮 = セレ, and so on. Other boomerang-shaped characters, like "く" or "ゝ" or "へ" were also used to express [n/m/ŋ] in various books at that time.

• The oldest book that has katakana "ン" as we know today is 法華経【ほっけきょう】 in 1058. Some books still used "レ, ゝ, く, へ" after this, but at around 1100, "ン" became popular.

• So the author believes this "ン" is not from a part of any (万葉) kanjis. He believes "ン" derived from this "レ" or V-like character, used to represent [n/m/ŋ] sound.