PICNIC is a phrase that members of the chat room like to say when a live stream goes down. Picnic is "panic" misspelled.
The story of PICNIC begins in early 2010. After about a dozen episodes of NSFW, there was one episode that had technical issues getting going. When the live stream failed, the chat room started posting "PANIC!" in rapid succession. Amongst the panic, a lone "PICNIC!" emerged from Patrick Delahanty. The meme developed and PICNIC became the universal signal of the shit stream hitting the fan.
In February 2012, popular Twitch streamer Jayson Love (MANvsGAME) appeared on episode 115 of NSFW (Man Hype Man). He later popularized the phrase on his own stream, which then spread across Twitch.
During the Twitch Town Hall event at PAX Prime 2014, the panicBasket emote was voted on by attendees during the annual global emote contest, and won.
So despite Night Attack not officially moving to Twitch until late 2016, Diamond Club has had a presence since Twitch's formative years.