けんけんごうごう and かんかんがくがく
kenken gougou and kankan gakugaku
Winding down the week of two-kanji yo-ji, we've got some high-level rare yo-ji with very similar meanings. We could have made this a triple by including 喧喧諤諤 (けんけんがくがく;kenkengakugaku*), but let me explain why we didn't after the definitions.
1. Pandemonius uproar
1. Heated arguing
2. Outspoken about one's beliefs (pushing the boundaries of politeness)
While I was planning out the line-up for this week's theme, I asked some of my friends for contributions, and one of them suggested 喧々諤々, but when I looked it up online, I came across a Japanese forum thread where someone was asking why 喧々諤々 doesn't show up in a 国語辞典. I looked it up in my 四字熟語辞典, and I couldn't find it either. One of the commenters in that thread pointed out that the reason it doesn't show up is because it's not a real 四字熟語. While both my Japanese word processing software and Rikai-chan recognize it (defining it as "tumultuous; everyone voicing their opinions at once), the fact of the matter is that it's an oral tradition, a verbal mangling of today's two. Take the first part of one, the last part of the other, and you've made yourself a brand new idiomatic expression.
If you're writing, I recommend using either 喧々囂々or 侃々諤, whichever suits your purposes. But since they're old and rare, if you want to say something in conversation, people today are much more familiar with the amalgamation: 喧々諤々.
You can follow any of these with the verbs する, or 言う to fit it into a sentence, or you can also use になる。
After that politician's remarks on the Amakudari system, the Diet erupted into pandemonium.
There's absolutely no cause for heatedly arguing politics or religion when you're talking to your mother-in law.
When I asked whether or not we should stay and wait to be rescued, or try to fight our way through the zombie hordes, everyone began shouting their opinion simultaneously. Man, the apocalypse is rough.
* post-post edit, thanks to Sash's watchful eye.