The Collaborative International Dictionary of English v.0.48:

Chrisom \Chris"om\, n. [See Chrism.]
   [1913 Webster]
   1. A white cloth, anointed with chrism, or a white mantle
      thrown over a child when baptized or christened. [Obs.]
      [1913 Webster]

   2. A child which died within a month after its baptism; -- so
      called from the chrisom cloth which was used as a shroud
      for it. [Obs.] --Blount.
      [1913 Webster]

WordNet (r) 3.0 (2006):

chrisom
    n 1: a consecrated ointment consisting of a mixture of oil and
         balsam [syn: chrism, chrisom, sacramental oil, holy
         oil]