Onomancy

from WordNet (r) 3.0 (2006)

onomancy
    n 1: divination by the letters of a name

from The Collaborative International Dictionary of English v.0.48

onomancy \on"o*man`cy\, n. [Gr. 'o`noma name + -mancy. Cf.
   {Nomancy}.]
   Divination by the letters of a name; nomancy. [R.] --Camden.
   [1913 Webster] Onomantic