When Thanos snapped his fingers in Avengers: Infinity War, half the life in the universe vanished in an instant. The latest official tie-in book has finally revealed that this is an event the world calls "The Decimation." It's a perfectly appropriate name, evoking memories of a similar tragedy that struck the X-Men in the comics.
Marvel has been carefully avoiding exploring the consequences of the snap, so as not to spoil any plot details for Avengers 4. With the sole exception of one of the post-credits scenes of Ant-Man & the Wasp, none of the movies have been set in this period. The Marvel Television shows have dodged the snap - even Agents of S.H.I.E.L.D., whose fifth season was heavily influenced by Thanos' attack. This silence has come to an end, however with the publication of Brandon T. Snider's The Cosmic Quest Volume Two: Aftermath. A young adult book, it doesn't go into great detail about the horror of it all, settling for throwaway references to the chaos that ensued on a global scale. But, for the first time, it officially reveals the in-universe name for the event fans have long been calling the "Snappening."
To the Earth's surviving population, the moment when half the life on the planet crumbled to dust is known as "The Decimation." The Avengers have kept the true cause of the snap a secret, perhaps figuring that knowledge of Thanos and the Infinity Stones would hardly help the world to heal. All the public really know is that, in an instant, they had to watch as their friends, neighbors, and loved ones turned to ash and blew away on the wind. The planet is grieving.
"The Decimation" is most certainly an appropriate term. It's lifted straight from the comics, where it usually refers to the horrific aftermath of the "House of M" event. That story saw the Scarlet Witch depower all but a tenth of the world's mutants. Countless depowered mutants died in the aftermath; some were left in hazardous situations, perhaps losing the power of flight while propelling themselves through the stratosphere. Many more committed suicide, unable to cope with the loss of what had been a core part of their identities.
The X-Men and the Avengers feared the world would be unable to cope with the knowledge that this was done by a single individual, and kept it secret. The similarities between these two Decimations are striking - both were initiated by a single being, transformed the world in one tragic instant, led to widespread suffering and grief, and were kept secret by the heroes.
Until now, fans have struggled to settle on a name for the snap. The most common has been the "Snappening," an amusing term that's designed to rid the moment of some of its horror. Now we finally have an official title - and it's one that works perfectly.