Source : Webster's Revised Unabridged Dictionary (1913)

Mavournin \Ma*vour"nin\, Mavourneen \Ma*vour"neen\, n. [Ir. mo
   mhuirnin my darling; mo my + mhuirnin darling.]
   My darling; -- an Irish term of endearment for a girl or
   woman. ``Erin mavournin.'' --Campbell.