Clean the octopus well. Boil the fennel in some water for 6 minutes, strain and finely chop. Slightly saute the spring onions in olive oil in a pot. Add the chopped octopus and 2 cups of water and simmer for about 50 minutes. Use a fork to check whether the octopus is done or not. Then extinguish with wine and add fennel, tomatoes, salt and 1 extra cup of water. Continue simmering and add some more water, if required. Add the olives 10 minutes before removing the food from heat. Sprinkle with abundant freshly ground pepper and serve warm.