The Collaborative International Dictionary of English v.0.48:

Sallet \Sal"let\ (s[a^]l"l[e^]t), n. [F. salade, Sp. celada, or
   It. celata, fr. L. (cassis) caelata, fr. caelare, caelatum,
   to engrave in relief. So called from the figures engraved
   upon it.]
   A light kind of helmet, with or without a visor, introduced
   during the 15th century. [Written also salade.]
   [1913 Webster]

         Then he must have a sallet wherewith his head may be
         saved.                                   --Latimer.
   [1913 Webster] Sallet

The Collaborative International Dictionary of English v.0.48:

Sallet \Sal"let\, Salleting \Sal"let*ing\, n.
   Salad. [Obs.] --Shak.
   [1913 Webster]

WordNet (r) 3.0 (2006):

sallet
    n 1: a light medieval helmet with a slit for vision [syn:
         sallet, salade]