1505-15; earlier: hedge or fence used as a boundary or protection, (v.) to enclose with a fence; compare Old Englishmund hand, hence protection, protector; cognate with Old Norsemund,Middle Dutchmond protection
1515, as a verb, "to fence in;" the noun is 1551, and originally meant "fence, hedge," now only dial. in that sense; commonly supposed to be from O.E. mund "hand, protection, guardianship" (cognate with L. manus), but this is not certain. Perhaps a confusion of the native word and M.Du. mond "protection," used in military sense for fortifications of various types, including earthworks, and infl. by mount (n.). Sense of "artificial elevation" (especially over a grave) is from 1726.