Okay, so there's a historical/religious definition that is a proper noun, and a casual derivation that is a regular noun.
Jehu-the-man has several factoids attached to his legacy. As follows: 1. Jehu was originally a commander of chariots for Ahab, king of Israel, 2. He eventually led a revolt and became king himself, 3. He is purportedly the king who had Jezebel killed in accordance with Elijah's prophecy. Lastly, it is noted that "he drives furiously" (II Kings 9:20)
By the 17th century and into 'modern' usage, jehu has come to mean a reckless coachman, or a fast (and unsafe) cab driver!
I first heard this word from a fellow bus passenger. The woman seemed older than God and had a complaint for everything, and hurled "you drive like Jehu!" at the bus driver as she disembarked!
Happy New Year
–C