1520s, from Middle French sombresault, from Old Provençal sobresaut, from sobre "over" (from Latin supra "over;" see supra-) + saut "a jump," from Latin saltus, from the root of salire "to leap" (see salient, adj.). Sometimes further corrupted to somerset, etc.

1845, from somersault, n.. Related: Somersaulted; somersaulting.