Meaning: return to the beginning; start again.
Example: If this experiment doesn’t yield the answer, we’ll have to go back to square one.
Origins: Various possibilities: English football broadcasts, board games, or hopscotch.

  (Definitions and origins.)

  (Examples.)

Rewrites: revisit square one back to “Start” back to launch time to reboot reset to zero
Discussion: I mainly worked with the board game scenario, since that seems to me to be the most apt metaphor.