The crook and flail are among the most famous symbols from ancient Egypt symbolizing the power and majesty of the king. Both these items were associated with Osiris and symbolized his early rule of the land. The symbols appear in the Early Dynastic Period during the reign of the first king, Narmer (c. 3150 BCE), and linked the king with the mythical first king of Egypt Osiris.
According to the myth of Egyptian God Osiris, Osiris’ kingdom was usurped by Set, who murdered him, but he was resurrected by his sister-wife, Isis. She bore him a son, Horus, who defeated Set and restored order to the land. The king was associated with Horus (with some exceptions) during life and with Osiris in death. Once Horus avenged his father and defeated Set, he took the crook and flail of his father to represent the legitimacy of his reign, and so it was for the kings of Egypt who identified with these gods.
The crook was an early tool used by shepherds while the flail was a means of herding goats and also harvesting an aromatic shrub known as the labdanum. Since Osiris was originally an agricultural/fertility deity, he was associated with both implements from the Predynastic Period and they served as reminders of the past and the importance of tradition as well as, obviously, symbols of the legitimacy and power of the king.