Ketevan is *not* the Georgian form of Katherine. That is incorrect.
The actual Georgian form of Katherine is: Ekaterine, written in Georgian as ეკატერინე (literally Ek'at'erine).
As for Ketevan, that name is actually of Persian origin - as many Georgian names are. It is ultimately derived from Katayun. See the entries for Katayun and Ketevan in the Submitted Names Database.