i

諱.　

I also examined this character in the glossary of Chinese character.

The sound of the character is "ki".
And as a custom of pronunciation，"i".

It had been so described.

Yes，"i" is "as a custom".
It is not formal sound of 諱.

訓(kun・When reading the character by the Japanese language).
This description also is not there.

Next 韋.
　
The sound of the character is "i".
There was no description of the other.

Pronunciation of 韋 is "i" to the last.
And this character show the sound of 諱.
　
So pronunciation of 諱.
It must be "i".　

Note:Today，character of 韋 is rarely used in Japan.
Example of the use of this character that I know.
It is the name of the military commander of the Three Kingdoms in China.
　
His name is 典韋.　
"Ten-i“ in the Japanese pronunciation of the current.　

典(last name).
韋(first name).


・・・・・・・・・
　
　
For example.　

諱 had been pronounced "i" originally.
And 忌 had been pronounced "ki".
　
At some point in time，諱 began to share the meaning with 忌.
(Little away from the original meaning of each other.
And it became a general meaning of each other.　

At the same time，諱 began to share the pronunciation with 忌.
(忌 also pronounce "i".)
　
And eventually，pronunciation of "ki" became dominate as pronunciation of this meaning.　
By contrast，pronunciation of "i" is no longer in use gradually.　
　
This might be such simply.
　
Note：Or meaning and pronunciation of 諱 has been absorbed into 忌.

　
・・・・・・・・・

　
Well，description of pronunciation of 忌.
　
The sound of the character is "ki".
When reading the character by the Japanese language.
It is "i-mu，i‐mawashī". (忌む，忌まわしい)

Yes，"i" is reading 忌 by the Japanese language.

Pronunciation of "i-mu(いむ)" of Ancient Japanese language.
It indicated the sense of 忌.

After introduction of Chinese characters.
Japanese began to read 忌 by the pronunciation of "i".
(Of course they also read it "ki".)

In short，"i" was the sound of Japanese.

Note:Before introduction of Chinese characters.
Character did not exist in Japan.