"to keep safe, preserve from loss or decay," late 14c., from Old French conserver (9c.), from Latin conservare "to keep, preserve, keep intact, guard," from assimilated form of com-, here perhaps an intensive prefix (see com-), + servare "keep watch, maintain" (from PIE root *ser- (1) "to protect"). Related: Conserved; conserving.
As a noun (often conserves) from late 14c. as "that which preserves;" early 15c. as "a confection, something preserved with sugar, etc."
It is the hypothetical source of/evidence for its existence is provided by: Avestan haurvaiti "to guard;" Latin servare "to guard, keep, watch;" Old Church Slavonic xraniti "to guard, protect;" Old High German gi-sarwi "armor, equipment," Old English searu "art, skill; wile, deceit."
"fruit preserved with sugar," c. 1600, from preserve (v.). Earlier it meant "a preservative" (1550s). Sense of "protected place for animals or plants" (a sense more properly belonging to conserve) is from 1807. The verb preserve in the sense of "maintain and reserve for special use in hunting or fishing" is from 1610s.