"Do a barrel roll" is a very famous Easter egg from Google. How to find it? And you enter this query into the search box and you will see it yourself. Well, if you are too lazy, then let me google it for you, like a haarica.
But the request did not become an easter egg right away and it did not come from the ceiling. The fact is that there is a series of games called Star Fox, in the first part of which the player controls a spaceship. And if the player performed a roll (this is such an aerobatics figure, during which the aircraft rotates about the longitudinal axis by 360 ° while maintaining the general direction of flight), then his transport became invulnerable for some time. The funny thing is that one of the main characters of the game, the commander of the armed forces of Corneria, the hare, General Pepper, constantly shouted in the game "Make a barrel!", Even if it was not the topic. One of the players got pretty sick of this and began to use this phrase on 4chan as a universal answer to questions like "What to do?"
On the Internet, the phrase is rarely used with any specific meaning, inserting it just for lulz. But one of the dictionaries claims that the phrase can still mean “a proposal to postpone things for a while and do something fundamentally different from what the author is asking about.”