Source : Webster's Revised Unabridged Dictionary (1913)

Somersault \Som"er*sault\, Somerset \Som"er*set\, n. [F.
   soubresaut a jump, leap, OF. soubresault, It. soprassalto an
   overleap, fr. L. supra over + saltus a leap, fr. salire to
   leap; or the French may be from Sp. sobresalto a sudden
   asault, a surprise. See {Supra}, and Salient.]
   A leap in which a person turns his heels over his head and
   lights upon his feet; a turning end over end. [Written also
   {summersault}, {sommerset}, {summerset}, etc.] ``The
   vaulter's sombersalts.'' --Donne.

         Now I'll only Make him break his neck in doing a
         sommerset.                               --Beau. & Fl.

Source : WordNet®

Somerset
     n : a county in southwestern England on the Bristol Channel