The Collaborative International Dictionary of English v.0.48:

Bairn \Bairn\ (b[^a]rn), n. [Scot. bairn, AS. bearn, fr. beran
   to bear; akin to Icel., OS., & Goth. barn. See Bear to
   support.]
   A child. [Scot. & Prov. Eng.]
   [1913 Webster]

         Has he not well provided for the bairn?  --Beau. & Fl.
   [1913 Webster]

WordNet (r) 3.0 (2006):

bairn
    n 1: a child: son or daughter

Moby Thesaurus II by Grady Ward, 1.0:

24 Moby Thesaurus words for "bairn":
   cherub, child, chit, darling, innocent, kid, kitten, lamb, lambkin,
   little bugger, little fellow, little guy, little innocent,
   little one, little tad, little tot, mite, nipper, offspring,
   peewee, shaver, tad, tot, wee tot