The Collaborative International Dictionary of English v.0.48:

Ogham \Og"ham\, n. [Ir.]
   A particular kind of writing practiced by the ancient Irish,
   and found in inscriptions on stones, metals, etc. [Written
   also ogam.]
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Ogam \Og"am\, n.
   Same as Ogham.
   [1913 Webster]