Mince the garlic. Trim the feathery tops from the fennel and cut the bulb lengthwise in half; cut out the core and coarsely chop the fennel into 1" pieces. Peel and slice the carrots 1/2" thick. Heat the olive oil in a soup pot over medium heat. Add the garlic, fennel, and carrots and saute until the vegetables are hot and sizzling, 3 to 4 minutes. Add the water, cover and simmer over low heat until the vegetables are barely tender, about 5 minutes. Add the tomatoes with their juices and break them up with a wooden spoon. Add the corn and kidney beans. Bring the liquid to a boil over medium heat. Add the marjoram and salt and pepper to taste. Reduce the heat to low and simmer, covered, until the flavors come together, about 30 minutes. Stir the macaroni and frozen spinach into the soup and simmer until the pasta is tender, about 10 minutes more. Remove the soup from the heat, stir in the parmesan and adjust the seasoning. Serve hot.