卜

卜 is a pictograph modeled after the cracks formed when the plastron (the underside shell) of a turtle was heated over fire for divination.

Ancient Chinese people heated turtle shells or ox bones in fire and interpreted the resulting cracks to predict good or bad fortune.

They would carve "option 1" on one side and "option 2" on the other side of the shell, then apply heat; the direction of the resulting crack was believed to reveal the will of Heaven.

Some say the pronunciation [bok] for 卜 comes from an onomatopoeic sound—the “pop” or “snap” noise made when the turtle shell cracks under heat.

It is believed that the ancient pronunciation was close to "pok."