Albert Barnes on Acts 2:12

Were in doubt. This expression--διηπορουν-- denotes a state of hesitancy or anxiety about an event. It is applied to those who are travelling, and are ignorant of the way, or who hesitate about the road. They were all astonished at this; they did not know how to understand it or explain it, until some of them supposed it was merely the effect of new wine.

(b) "What meaneth this" Acts 17:20