"Did 'Ba Gua' originate at the Shaolin temple?"
No. Ba Gua originated somewhere in southern China, and for the life of me, I can't remember where. But, the interesting thing about this, is that it's more related to Taoism than Buddhism, and it's moves are more Tai Ji oriented than they are gong fu. It is a style which is performed slowly, in high stances, with many movements along prescribed circular patterns on the floor. (As opposed to gong fu, which tends to be in a linear pattern). It is not practiced all that much at Shaolin.