The name "collard" is a corrupted form of the word "colewort" (cabbage plant).
They also explain that
The cultivar group name Acephala ("without a head" in Greek) refers to the fact that this variety of Brassica oleracea does not have the usual close-knit core of leaves (a "head") like cabbage.
I thought that perhaps this is why they are called acelga here. I honestly do not even know if the acelga here is collards, but the acelga is closer to a collard than any of the other greens I know. Brassacas are the family that includes broccoli, cauliflower, cabbage, kale, and the like.
The leaves are thicker than most of the other greens, and usually a little bit bitter, with lots of flavor. In my opinion, they are way better than chard, which is what people in the north seem to prefer. They are eaten and grown year round in many places, and taste best after a bit of cold weather. I love them with ham hocks, smoked pork or a little bit of bacon, with sometimes some potato thrown in the pot. I always put vinegar in them, sometimes a little bit of sugar.