late 14c., preserven, "keep safe or free from harm," also "act so as to insure that something does not occur," from Anglo-French preservare, Old French preserver, Medieval Latin preservare "keep, preserve," all from Late Latin praeservare "guard beforehand," from Latin prae "before" (see pre-) + servare "to keep safe" (from PIE root *ser- (1) "to protect").
From early 15c. as "maintain, keep in a certain quality, state or condition." Of fruit, etc., "prevent from spoiling by use of preservative substances," 1570s; of organic bodies, "keep in existence or alive," from 1610s. Related: Preserved; preserver; preserving.