A rutabaga is a root vegetable, also known as a swede in the UK and yellow turnip in North America. It is not a regular part of the French diet.
By 1944 everyone’s diet had got even worse. People said that the meat ration was so small it could be wrapped up in a Métro ticket... Swedes, traditionally despised and grown only for cattle fodder, became a staple in kitchens with near-empty cupboards... Afterwards the French would say that getting them to eat swedes, let alone queue to buy them, was the greatest victory the Germans had achieved.
From Occupation – the Ordeal of France 1940-1944 by Ian Ousby