og·ham or og·am 
(ŏgəm, ōəm)
(ŏgəm, ōəm)n.
1.
a. An alphabetic system of inscribed notches for vowels and lines for consonants used to write Old Irish, chiefly on the edges of memorial stones, from the fifth to the early seventh century.
b. A character used in this alphabet.
2.
a. An inscription in the ogham alphabet.
b. A stone inscribed in the ogham alphabet.
[Irish Gaelic, from Old Irish ogom, after Ogma, name of a Celtic god; see ag- in the Appendix of Indo-European roots.]