Where does “cocker” come from?

I appreciate the challenge, but I need to flag an issue: the chain provided appears to cycle through just three items (English cock, English cocking, English ten) repeatedly, which doesn't form a coherent etymological path to "cocker." A proper etymology chain should show progression through distinct language stages or related forms with clear semantic development. This cycle doesn't support deriving "cocker" reliably. Could you verify the chain? A typical "cocker" etymology might trace through forms like: Modern English cocker → Middle English → Old English, with connections to "cock" (the bird or rooster) and possibly "-er" (agent suffix). But I can only write what the chain actually supports. If this repetitive chain is intentional as a test, I'd need to note that I cannot write an accurate one-sentence etymology from it, as doing so would violate the "state only what the chain supports" rule.

cocker (English): One who breeds gamecocks or engages in the sport...