User blog comment:FeaturedMe/Feat's Anime Review - Episode 150/@comment-4933386-20120929090327/@comment-78.250.188.99-20120929091835

The Oracion Seis all have code names but so far, we only know about Hoteye's one (Richard) and now, Cobra's, which kinda suits him even if it's still weird... I wouldn't say it's Mashima's choice, as it was in a filler arc, though. But something like that has to be canon, surely the anime team asked Mashima about it (it's so nice he decided to tell Kinana only ^^ )