A ton of people in HTTYD have monikers, i.e. Stoick the Vast, Gobber the Belch, Dagur the Deranged, etc. I think Hiccup should have one too. And not anything like Hiccup the Dragon Tamer, naw that's too pedestrian.
And it's clear as the series progresses that he's not the first viking to refuse to kill a dragon or to ride one, and while he's is the only one to push for that change Archipelago wide instead of keeping it a secret/Berk only like many of the other tribes [Wing Maidens, Defenders of the Wing, his mom, etc.]
He did it through months and years of sheer determination and grit. It was work to get vikings and dragons on the same page. The peace he fought tooth and nail for came with days and nights of fighting and being as ruthless with his ambitions for peace as Viggo claimed him to be. Viggo was right, Hiccup is ruthless, just not violently so, Hiccup sets a goal and accomplishes it hell or high water.
He set out to shoot down a Night Fury? He did it. Made a goal to learn/befriend said dragon. He did it. Kill the Queen? Done. Show his village dragons aren't so bad when they're not also fighting for survival? It took a few, heh, hiccups, but he got there! Defeat the Dragon Hunters? Hell yeah he did.
The most important character trait Hiccup has in my opinion, is despite being a hiccup, despite being small and weak and overall not good at the tradition viking way, despite all the cards stacked up against him from even before he was born [he was premature!!!] he never gave up. If a plan didn't go his way, he pivoted, came from it at a different angle, got advice from those who listened [Toothless, Astrid, Gobber, his dad, etc], he learned and tried again.
One would say he was relentless. Ruthless.
I personally think his viking moniker should be Hiccup the Relentless - though I am partial to Hiccup the Ruthless. These words conjure up a violent picture, and it would be funny narratively speaking for enemies/strangers to look at the green bean and go "Relentless? Ruthless? Lol, I can snap him like a twig!" and they would be right, you can snap him like a twig [just gotta get passed Toothless to do it lol]. Most important it could be an in-joke to him and his allies/friends. Hiccup is those traits, just not violently so. He's kind, compassionate, empathetic, and always there with a helping hand because that's just who Hiccup is.
extra points if Snotlout says it as a joke/jab and the twins pick it up and it somehow sticks. Extra bonus points if Hiccup hates it/is annoyed by it at first, but it grows on him.