But of course. Everyone knows that Cockneys are evil, and that Orcs are fond of rhyming slang.
Actually, Orc English looks to me rather more like a generic English thug dialect. I don't think it's supposed to represent one group in particular. Tolkien tries to make their language as rough, brutal and uncivilised as he can, and just happens to end up with something Londonish (actually more Saaf Lundun than Cockney). All a complete coincidence, I'm sure.
