One IRC user explained their choice of words to The Daily Dot:
There really is nothing too exciting about the meaning, sorry to say. We chose it because it was clever, had semi-subtle offensive overtones, and wasn't as childish as our second choice of KFCBUTTSEX
Furthermore, if there was any overt justification for why we chose gas chambers, it’s because we wanted to reference Hitler, who’s [sic] gas chamber antics are always offensive to people. His name was mentioned a lot when we were discussing what to spell.
The phrase, "KJU GAS CHAMBERS" refers to the North Korean leaders mysterious and brutal prison camps, where entirely families have reportedly been gassed.
Mashable reported December 3 that 4chan was planning to spell out the phrase after they propelled Kim to the top of the poll. "For our Glorious Leader, Episode II: We've already voted him to the top, now lets spell something nice with the first letters of the contestants," wrote one user.