Babel

Parents today would certainly be astonished and mostly appalled to hear that their offspring would be manured at school, since they would probably be afraid of the stench coming off their children.

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In the times of James Murray (A New English Dictionary on Historical Principles, Oxford, 1888-1928) the manuring of students was something much desired by parents, since it meant to 'cultivate, train the mind or body'.

Other sources claim that the word manure is derived from Latin 'manus' and thus denotes any action proceeded with one's hands. So a cook might well be industriously manuring in the kitchen!