“No Lackin” as in “I’m not lacking a gun.”
According to Know Your Meme:
“No Lackin Challenge is a video fad in which people film themselves brandishing firearms and pointing the weapons at unsuspecting victims to provoke them into displaying a firearm in return. The game is meant as a way to test the readiness of people who are living in high crime areas.
According to the HipWiki, the slang expression “no lackin” was initially popularized among Chicago gang members. On June 13th, 2012, rapper Lil Mister released a song titled “No Lackin.”
On August 15th, 2014, Urban Dictionary user Been Krill submitted an entry for “No Lackin,” defining the term as “Not having a firearm on you.” The exact origin of the “No Lackin” challenge is unknown. The earliest known example was uploaded by YouTuber Chase BanzVIDEOS in a video titled “Never Get Caught Lacking in Chicago ‘Challenge’” on September 11th, 2017.”
Yet according to Snopes, this is not a real thing (they say it is “unproven”):
“Teenagers are participating in a dangerous new internet craze known as the “No Lackin Challenge,” and a Memphis boy was shot in the head during an instance of the fad gone awry.
Early, local reports of the incident didn’t describe the shooting as related to the No Lackin Challenge. The internet fad apparently involves participants drawing guns on one another; in the context of the No Lackin Challenge, “lackin” is purportedly a Chicago-area colloquialism defined as being caught without a firearm.”
No matter the case for the origin or validity of this challenge, it appears that this is a thing, as evidenced by the videos on YouTube.
Play stupid games, win stupid prizes.