Middle English muk, probably of Scandinavian origin: compare with Old Norse myki 'dung', from a Germanic base meaning 'soft', shared by meek.

• English muck is from an early Scandinavian word that goes back to a ancient root meaning ‘slippery, slimy’ from which mucus (mid 17th century) also descends. The verb first meant ‘to clean muck from’ and ‘to spread manure’, from which we get muck up or make a mess of and muck around, ‘to behave in a silly or aimless way’. Down-to-earth northerners might often comment that where there's muck there's brass. This form of the proverb, using brass in the sense ‘money’, is recorded in print only from the 1960s, but an earlier version was where there's muck there's money. The Australians introduced Lady Muck and Lord Muck at the beginning of the 20th century as names for a socially pretentious woman or man. The first muckraking was done by poor people, who would collect manure from the filthy streets of the city in the hope of selling it or finding something valuable. Since the start of the 20th century it has been used for searching out and publicizing scandal about people. Mucker or ‘friend’ was originally military slang, first recorded in the 1940s. It probably comes from the idea of a friend being a person who ‘mucks in’ or shares tasks cheerfully.