patronomatology

from The Collaborative International Dictionary of English v.0.48

Patronomatology \Pa`tro*nom`a*tol"o*gy\, n. [Gr. path`r,
   patro`s, a father + E. onomatology.]
   That branch of knowledge which deals with personal names and
   their origin; the study of patronymics.
   [1913 Webster]