In the Jewish faith you are not supposed to write or utter Gods name. A proffesor of mine told me some of his Jewish students would even write it like that on papers.
One of my philosophy teachers was Jewish and he explained that to write “God” on something made that something holy. We don’t treat what is holy as we do the ordinary (throw away a paper, erase a chalk board). Therefore, some chose to go with “G-d” instead of “God” to make the distinction.
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