The Collaborative International Dictionary of English v.0.48:

Meum \Me"um\, n. [L., neut. of meus mine.]
   Lit., mine; that which is mine; -- used in the phrase meum et
   tuum, or meum and tuum; as, to confound meum and tuum, to
   fail to distinguish one's own property from that of others;
   to be dishonest.

         Ancestors . . . generally esteemed more renowned for
         ancient family and high courage than for accurately
         regarding the trifling distinction of meum and tuum.
                                                  --Sir W.
                                                  Scott.
   [Webster 1913 Suppl.]