From Frankish *wītan (to know the way), via Old French — a guide is one who has knowledge of the path.
From Old French 'guider' (to lead), from Frankish *wītan (to show the way), from Proto-Germanic *wītaną (to know). A guide is one who 'knows the way.' Key roots: *wītaną (Proto-Germanic: "to know, see").