About

Origin

The term /b/lackup originated on 4chan's /b/ boards, during the so-called "Habbo Wars". These were organized raids by Anonymous, who would create a black avatar wearing a grey suit and an afro hairstyle, they would then go and block the entrance to the pool, a popular zone in Habbo Hotel. When there weren't enough /b/rothers to create the blockade, one would post a topic on /b/ requesting /b/lackup, i.e., help from fellow /b/rothers.
This derived in a "demotivational" poster, with two of the avatars used for the raids high-fiving.
"Habbo Wars"

Use

The image/phrase, or a combination of the two, are often used on 4chan when Anonymous needs a massive amount of people to complete a task; most often in raids or when trolling other 4chan boards. /b/lackup can also be requested when /b/ is trying to trollvote in a poll.