The Collaborative International Dictionary of English v.0.48:

Biestings \Biest"ings\, Beestings \Beest"ings\, n. pl. [OE.
   bestynge, AS. b[=y]sting, fr. b[=y]st, beost; akin to D.
   biest, OHG. biost, G. biest; of unknown origin.]
   The first milk given by a cow after calving. --B. Jonson.
   [1913 Webster]

         The thick and curdy milk . . . commonly called
         biestings.                               --Newton.
                                                  (1574).
   [1913 Webster]