Source : Webster's Revised Unabridged Dictionary (1913)

Octa- \Oc"ta-\
   A prefix meaning eight. See {Octo-}.

Octo- \Oc"to-\, Octa- \Oc"ta-\ [L. octo eight, Gr. ?, with a
   combining form ?. Cf.{Eight}.]
   A combining form meaning eight; as in octodecimal,
   octodecimal, octolocular.