c.1400, "to cultivate land," also "to hold property," from Anglo-Fr.
meynoverer, from O.Fr.
manouvrer "to work with the hands," from M.L.
manuoperare, from L.
manu operari, from
manu, abl. of
manus "hand" (see
manual) +
operari "to work, operate" (see
operation). Sense of "work the earth" led to "put dung on the soil" (1599) and to the current noun meaning "dung spread as fertilizer," which is first attested 1549. Until late 18c., however, the verb still was used in a fig. sense of "to cultivate the mind, train the mental powers."
"It is ... his own painfull study ... that manures and improves his ministeriall gifts." [Milton, 1641]