Source : Webster's Revised Unabridged Dictionary (1913)

Tilly-vally \Til"ly-val`ly\, interj., adv., or a.
   A word of unknown origin and signification, formerly used as
   expressive of contempt, or when anything said was reject as
   trifling or impertinent. [Written also {tille-vally},
   {tilly-fally}, {tille-fally}, and otherwise.] --Shak.