The Collaborative International Dictionary of English v.0.48:

Farthingale \Far"thin*gale\, n. [OE. vardingale, fardingale, fr.
   OF. vertugale, verdugade, F. vertugade, vertugadin, from Sp.
   verdugado, being named from its hoops, fr. verdugo a young
   shoot of tree, fr. verde green, fr. L. viridis. See
   Verdant.]
   A hoop skirt or hoop petticoat, or other light, elastic
   material, used to extend the petticoat.
   [1913 Webster]

         We'll revel it as bravely as the best, . . .
         With ruffs and cuffs, and farthingales and things.
                                                  --Shak.
   [1913 Webster]

WordNet (r) 3.0 (2006):

farthingale
    n 1: a hoop worn beneath a skirt to extend it horizontally; worn
         by European women in the 16th and 17th centuries