Meaning
Back to the beginning, to start again.

Origin
There are three widely reported suggestions as to the origin of this phrase: BBC sports commentaries, board games like snakes and ladders and playground games like hopscotch. Let's examine them in turn:

BBC Commentaries: In order that listeners could follow the progress of football games in radio commentaries, the pitch was divided into eight notional squares. Commentators described the play by saying which square the ball was in. The Radio Times, the BBC's listings guide, referred to the practice in an issue from January 1927.

Board Games: Many people report that the phrase refers to Snakes and Ladders or similar board games. The earliest citation of the phrase in print is currently 1952, from the Economic Journal:

"He has the problem of maintaining the interest of the reader who is always being sent back to square one in a sort of intellectual game of snakes and ladders."

Hopscotch: This playground game is played on a grid of numbered squares. The precise rules of the game vary from place to place but usually involves players hopping from square to square, missing out the square containing their thrown stone. They go from one to (usually) eight or ten and then back to square one.

From: http://www.phrases.org.uk