Topo*nym"ic

from The Collaborative International Dictionary of English v.0.48

Toponymy \To*pon"y*my\, n.
   A system of toponyms; the use of toponyms. -- {To*pon"y*mal},
   {Top`o*nym"ic}, {Top`o*nym"ic*al}, a.
   [Webster 1913 Suppl.]