'Fro' in the Bible

And a ferry boat passed to and fro to carry over the king's household, and to do what he thought good. And Shimei the son of Gera fell down before the king as he was just crossing over the Jordan.

And the king saith unto Joab, head of the host that is with him, 'Go to and fro, I pray thee, through all the tribes of Israel, from Dan even unto Beer-Sheba, and inspect ye the people -- and I have known the number of the people.'

And they go to and fro through all the land, and come in at the end of nine months and twenty days to Jerusalem,