The Collaborative International Dictionary of English v.0.48:

Math \Math\ (m[a^]th), n. [AS. m[=ae][eth]; akin to m[=a]wan to
   mow, G. mahd math. See Mow to cut (grass).]
   A mowing, or that which is gathered by mowing; -- chiefly
   used in composition; as, an aftermath. [Obs.]
   [1913 Webster]

         The first mowing thereof, for the king's use, is wont
         to be sooner than the common math.       --Bp. Hall.
   [1913 Webster]

WordNet (r) 3.0 (2006):

math
    n 1: a science (or group of related sciences) dealing with the
         logic of quantity and shape and arrangement [syn:
         mathematics, math, maths]