Unknown; likely a modern invented name or surname derivative.
Jex is a contemporary coinage with no established etymological root. It likely emerged as a creative variation of names like Jax or Rex, or as a transfer of the English surname Jex, which may have roots in the medieval name Jack or Geese.
Lead singer of the heavy metal band Jex Thoth
US births per 5-year period, 1990–present (SSA data).