Apparently in Arabic, there is no "guh" sound. I learned this a long time ago when I was ordering myself a silver necklace that was to say Gwen. I had the choice of them spelling it like J-wen or like Quin. I chose the latter.
Last week we called in take-out from Tandoori, the restaurant very near our house. I placed the order, they asked my name and I told them Gwen. They spelled it the best way knew how.