The Collaborative International Dictionary of English v.0.48:

Metronymic \Met`ro*nym"ic\, a. [Gr. ?; ? mother + ?, for ?
   name.]
   Derived from the name of one's mother, or other female
   ancestor; as, a metronymic name or appellation. -- n. A
   metronymic appellation.
   [1913 Webster]

WordNet (r) 3.0 (2006):

metronymic
    n 1: a name derived from the name of your mother or a maternal
         ancestor [syn: matronymic, metronymic]