Is there a metaphorical meaning for the word "Oysters" in this context? Or is it just a random animal came to his mind. I have no idea how the situation relates to oysters.
When I first came to Ceylon my Tamil friend A. chaffed me about my way of calling him and the rest of the population, whether Tamil or Mahomedan or Cinghalese, all indiscriminately natives, "as if we were so many oysters!" I told this to Ajax, and of course there was nothing for it after that but to call them all oysters !
Adam's Peak to Elephanta (1892)