I think, Todder is Toad , mentioned in season one. (In novels, Toad's full name is Todder)
If Toad is a builder, why go to Hardhome with Jon. He's a fighter if he's assigned to builders. Could the actor play Duncan, Jon yells "Duncan, keep in line" at Hardhome. --Mesmermann (talk) 20:05, June 3, 2015 (UTC)
Despite the fact that Toad is a builder, it is assumed that he went to Hardhome out of Jon's need for men to assist him.