[@RisqueBoots]

It's not too hard in concept: win a good number of fights, go on successful raids, be a good hunter, don't die in the process. In practice, it can be quite difficult. As such, those male goblins who are successful at those things are seen as good sires for strong children. 

Just keep the specifics away from the public forum if anyone 18+ wanted to RP that sort of thing.