1) Usually the dung of farm animals, mixed with straw and other bedding matter.
It was a valuable asset, employed by farmers to fertilise the land: 1483 to haue a lafull gait ... with ther muke & ther corne to and fro, Ovenden
1532-3 the seyd Nycholas ... to leyf the seyd howses as he finds them ... & to leff hys muk at the ende of hys terme, Bradfield
1555 to ... my sonnes all mucke and maner [manure] that is at the house, Knottingley. It may have been refuse or offal in other circumstances, as in York: 1538 Item rassavyd ... for the moyke at the Fyshe Lendyng, ijs viijd, St Michael, Spurriergate. This is likely to have been fish offal which would also serve as a fertiliser. The verb meant to remove muck from stables, now more usually ‘to muck out’: 1642 when they come backe they fall to mucking of the stables, Elmswell. It had numerous attributive uses, especially in the names of the tools used to handle it and the vehicles which transported it into the fields. These are dealt with individually below.