WARNING: The following article contains spoilers for Thor #10 by Jason Aaron, Mike Del Mundo, Marco D'Alfonso and Joe Sabino, in stores now.
For as long as we've known him, Thor has been the God of Thunder. Wherever he goes, lightning follows, a power that has positioned him as a literal god among men, and one of the strongest Avengers. The "God of Thunder" moniker is synonymous with the character, one not only used by fans, but by the characters he shares the page with. And while its origin may seem obvious, apparently, it's not referring to what you've likely assumed.
In Jason Aaron and Mike Del Mundo's Thor #10, the secret origin of the "God of Thunder" title is finally revealed. Despite what we all believed, it didn't start out as a play on his power to command the storm. It was an insult, one devised by Thor's father, Odin.
Thor #10 is an issue told from the point of view of the All-Father. With Asgard left in nothing but ruins and the cosmos on the edge of the War of the Realms, Odin is broken and angry. He's a hardened man, one who has seen more than his fair share of war. His relationship with his son Thor has always been difficult, as evidenced by the fight between the two that takes place in this issue, and while Odin feels love for his fierce son, he can't bring himself to say as much. Instead, he lashes out.
As he faces his son, Odin's narration reveals the secret origin of Thor's title; when he was just a baby, Thor was actually terrified of storms. He would cry every time the rain came, something Odin saw as a sign of weakness. Because of this, he first started calling his sone the God of Thunder as an insult, one borne "out of mocking contempt," in his own words.
Perhaps it was this connection to the storm that would lead Thor to becoming the god he now is. Or perhaps even then, the rain came from his wailing. Either way, as Odin himself states, Thor grew into the name, and now the lightning lives through him, and his power knows no equal.
Odin may not have known this at the time, but his mockery would eventually turn into one of the most widely recognized titles in the Marvel Universe.