"It is manna". Hebrew. man-hu. " What is that? for they knew not what 'that' was". See on Exodus 16:31.
wist. knew. From Anglo-Saxon, witan, to know.
it. that.
This. that.
Related Commentaries of Exodus 16:15
Exodus 16:15
15 And when the children of Israel saw it, they said one to another, It is manna: for they wist not what it was. And Moses said unto them, This is the bread which the LORD hath given you to eat.