From Greek xenos, meaning "stranger," "guest," or "foreigner."
Xeno arrives from ancient Greek with remarkable philosophical freight. The root "xenos" (ξένος) held a trinity of meanings in classical Greek: stranger, foreigner, and guest — three concepts that the Greeks understood as inseparable, bound together by the sacred institution of xenia, the hospitality code that governed relations with outsiders. To welcome a xenos was a religious obligation; Zeus himself was sometimes called Zeus Xenios, protector of guests and travelers.
A name meaning "stranger" was thus also a name invoking the highest ideals of welcome and protection. Several notable figures bore forms of this name in antiquity. Xenophon, the Athenian soldier and historian who chronicled the famous retreat of the Ten Thousand in his Anabasis, gave the root enduring literary prestige.
Xenocrates was a prominent philosopher who led Plato's Academy after Speusippus. The Stoic philosopher Zeno of Citium — whose name is simply a Hellenized variant — founded one of antiquity's most influential philosophical schools. The root also generated an enormous English vocabulary: xenophobia, xenon (the element named for being chemically aloof, a "stranger" among reactive gases), xenolith.
As a standalone given name in the modern era, Xeno is extraordinarily rare, which is precisely its appeal for parents seeking something that sounds both ancient and strikingly contemporary. It resonates with science fiction culture — androids, aliens, and expansive cosmologies frequently feature names with this root — while retaining genuine classical grounding. The name is also associated with the Xeno of Elea (more commonly Zeno), whose paradoxes of motion have tantalized philosophers for 2,500 years. Choosing Xeno is choosing a name that has always been just outside the mainstream, a stranger among names — which, given the etymology, seems entirely appropriate.