Most names I come up with for places are either very serious or just plain 'proper' for the region and culture. Many are descriptive, though sometimes colorfully rather than plainly (such as the Shadowmarch Wood, which could've been more simply named the Dark Wood frex).
A few are intentionally silly or kinda cheesy, but generally just if I think it's fine that the locals or some famous bard might've named the place humorously. Haven't used silly place names in a while now, though, far as I can recall.... I don't think I've actually used a terribly cheesy or silly name for any particular place though while DMing.... *ponders*
Lessee, some examples from my Rhunaria site:
General regions/main features: A mountain range called the Impassable Wall of I'Ratha, an unexplored ocean called Sea of the Dark Mist, a lake named the Elfindeep, a ruined land called the Wastelands of the Fallen, plains called the Bloodgrass Fields but formerly known as the Summer Fields, highlands/plateaus called the Drake-Den Cliffs, woods called the Firefly Forest, and there's the Tikaminari Jungle.
Duchy of Baram geography: Haz-Ireth Yulam (Woodlands of Yulam), Veiled Forest, River of the Winding Way, Falrem Onarra (Falrem's Lifeblood, a river), Roc Roost Peak (a mountain), Scarlet River.
Vicinity of Agrhk'Mar Trelgmhk, the hobgoblin-founded 'free city of Trelg': Fnar'Tng Dgr (Broken-Crest Hills), Trelg'Hrandag Ruhr (Trelg Dedication Park), Dgrtuz Zoag (Hillsroad South).
Ur-Dalechron Hegemony's area, mostly dwarven lands: Icaea tol Dalmarius Renata (Lake of Dalmarius' Respite), Magna Icaea tol Vikona Mida Pila (Sea of Broken Spears), Pyral Sarnus (Ashen Desert), Archaius Divis Verdalis (Old Valley Woodland, Uru'Gelath Talianor in Elven speech), Minata Icae tol Aevinarnoch (River of Elvenshade, Elure Estarin'Saeid in Elven speech), Raug Dras'Ir Paz-Nyk (a river in Orcish territory, meaning unknown to dwarves), Viscar tol ven Nochta Divitas (Venom of the Shadow Gorge, a river).