Here are some possibilities:
* Jealous court officials: Those who had lost favor with Daniel due to his righteousness and wisdom might have spread this rumor to see him removed from power.
* Religious leaders: The Jewish religious leaders, who were opposed to Daniel's faith and influence, may have been motivated to spread the rumor.
* Enemies of the king: Individuals who opposed Darius' rule might have spread the rumor to destabilize the kingdom.
It's important to remember that this story is a biblical narrative, and its focus is on Daniel's faith and God's miraculous deliverance. The story doesn't provide specific details about the origin of the rumor.