Ogham

Ogham or Ogam, an alphabet of 20 letters in use among the ancient Irish and Celts, found carved on monumental stones in Ireland, Wales, Cornwall, and the North of Scotland.

Definition taken from The Nuttall Encyclopædia, edited by the Reverend James Wood (1907)

Ofterdingen, Heinrich von * Oglethorpe, James Edward
Oehler, Gustav
Œil-de-bœuf
Œland
Œnonë
Oersted, Hans Christian
Oesel
Offa's Dyke
Offenbach, Jacques
Offertory
Ofterdingen, Heinrich von
Ogham
Oglethorpe, James Edward
Ogowe`
O'Groat's House, John
Ogyges
Ogygia
Ohio
Ohio River
Ohm, Georg Simon
Ohnet, Georges
Oil City