Some sort of derivation from *déḱm̥t(“ten”) (with Pre-IE *d lost or merged with *h₁ in the same way the initial dental obstruent was lost in the oblique cases of *dʰéǵʰōm(“earth”)), perhaps its ordinal number (*déḱm̥t + *-ó-). If so then this could come from some phrase, "tenth", whose substantive noun can only be conjectured.
Proto-Balto-Slavic: *śímtan < (< *ḱḿ̥tom) (see there for further descendants)
Proto-Celtic: *kantom (see there for further descendants)
Proto-Germanic: *hundą (see there for further descendants)
Proto-Hellenic: *hekətón (see there for further descendants)
Proto-Indo-Iranian: *ćatám (see there for further descendants)
Proto-Italic: *kentom (see there for further descendants)
Proto-Tocharian: *känte[1] (see there for further descendants)
References
Sihler, Andrew L. (1995) New Comparative Grammar of Greek and Latin, Oxford, New York: Oxford University Press, →ISBN
^ Adams, Douglas Q. (2013) “kante”, in A Dictionary of Tocharian B: Revised and Greatly Enlarged (Leiden Studies in Indo-European; 10), Amsterdam, New York: Rodopi, →ISBN, pages 146-147
