From the Greek name Ζήνων (Zenon), which was derived from the name of the Greek god Zeus (the poetic form of his name being Ζήν). Zeno was the name of two famous Greek philosophers: Zeno of Elea and Zeno of Citium, the founder of the Stoic school in Athens.
People with the name Kellen have a deep inner desire to use their abilities in leadership, and to have personal independence. They would rather focus on large, important issues, and delegate the details.