Help Identify Wacky Grip

So, I like weird guns and gun bits. A local shop has an AR-15 with a wacky grip on it. It wraps up and connects to where you'd attach a regular trigger guard for a lower that didn't have one built in.



Does anyone here happen to know the proper name for this type of grip? The shop guys say it's a bump fire grip.

Thanks in advance,
Hard Eight