SERVI. This name was given by the Romans to their slaves; they were so
called from servare, to preserve, from the ancient practice of the generals
of the army, who were accustomed to sell their captives, and preserved them
rather than kill them: servi autem ex eo appellati sunt, quod imperatores
captivos vendere, ac per hoc servare, nec occidere solent. Inst. 1 3, 3.