Why does 「G」 stand for "excessive depiction of violence" (on ニコニコ)?


The website [ニコニコ](https://seiga.nicovideo.jp/) marks manga with sexual
content with the letter H and with excessive depiction of violence with the
letter G. If you really feel the need to see an example, [this
manga](https://seiga.nicovideo.jp/comic/35998) is marked with both. In the
desktop version, there is an explanatory text beside them, reading 性的な描写 and
過激な暴力描写 respectively, but on the mobile version there is no such explanation,
only the letters.

I understand why "H" is used for sexual content, but I don't know why they
chose "G" for "excessive depiction of violence". 暴力 _bōryoku_ "violence"
starts with "B", 過激 _kageki_ "excessive" with "K" and there is also no English
word that I can think of. The only thing with "G" would be the 激 of 過激. This
could be a shift "excessive => excessive violence", just like for the English
words "explicit" and "graphic". I have only seen "G" as euphemism for ゴキブリ
cockroach, and searches for "G"+暴力 or "G"+"過激" yield no relevant results.

This leads me to two related questions: Firstly, would a Japanese speaker
recognize what "G" as a warning meant without the explanation? And secondly,
why did niconico chose "G"? I am kind of hoping for an interesting story like
behind the "H", but maybe it was just an arbitrary choice with not much
thought behind it.




When I saw the mark of G, I didn't understand why G is used.  
I thought of ゴキブリ and gravity.  
But after several seconds, I got an idea.

I think G means グロ(グロテスク).  
This is a common word used like グロ画像, エログロ, グロ注意, グロい.  
グロい means disgusting or gross, though it's not used only for violence but also
for worms, injuries, excretas and as an internet slang so miserable scenes.

Now I found this page. (There are no disgusting images or videos)  
Some people on the Internet seem to use G as グロテスク.  
<https://dic.pixiv.net/a/R-18G>




It's almost certainly グロ, an abbreviation of グロテスク.

