The Collaborative International Dictionary of English v.0.48:

Prattle \Prat"tle\, v. i. [imp. & p. p. Prattled; p. pr. & vb.
   n. Prattling.] [Freq. of prate.]
   To talk much and idly; to prate; hence, to talk lightly and
   artlessly, like a child; to utter child's talk.
   [1913 Webster]