There was an old or even ancient superstition in Russia about bears (of course we do obsessed with bears): it is a bad omen to call a bear by "his name". Here "his name" stands for the word "bear" (медведь). If you will "call" the bear i.e. pronounce the word "bear" the bear can think that you are calling him and come to you. As a result there are only few possibilities: you can became the bear's breakfast, lunch or dinner. So there is a tradition to use nicknames for bears instead of the word "bear". There are plenty of them: Михайло Потапыч, Топтыгин, Косолапый etc. There is no any other animal in Russia which has so many nicknames.
Maybe using "G-d" is somewhat similar to this. People don't call the "God" without an extremely need.