Why is the ninth month called September?
late 14c., from Old French preservatif and directly from Medieval Latin praeservativus, from stem of praeservare (see preserve (v.)). The noun is from early 15c., "a preservative medication;" sense of "chemical added to foods to keep them from rotting" is from 1875.
preservative pre·ser·va·tive (prĭ-zûr'və-tĭv)
A substance added to food products or to organic solutions to prevent decomposition due to chemical change or bacterial action.