Green’s Dictionary of Slang

mum! excl.

an excl. demanding silence.

1523–4		Skelton ‘Garland of Laurel’ in Henderson Complete Poems (1948) 383: There was among them no worde then but mum!
1568		U. Fulwell Like Will to Like 11: Well, godfather, no more words but mum!
1590		Three Lords and Three Ladies of London J 2: But, mum, no words of it.
1607		Tourneur Revenger’s Tragedy (1967) IV i: Mum, For there’s a doom would make a woman dumb.
1611		Davies of Hereford Scourge of Folly 102: No more, peace; mumme.
1628		R. Speed Counter-Rat F: Mum then, — I’ll take a nap o’th’ boords Sir.
1632		R. Brome Covent-Garden Weeded IV i: Mum, hold your tongue still in your mouth, lest I halifax it with your teeth.
1640		The Wandering Jew 18: Our yong Cockney laughed, shook his head [...] and so without so much as mum, sneaked away.
1654		New Brawle 4: [B]ut mum, here she comes to speake for herselfe.
1663		A. Cowley Cutter of Coleman-street (1721) 765: Mum – not a Word.
1672		Wycherley Love in a Wood III i: Mum, mum, make no excuses man.
1678		Behn Sir Patient Fancy I: I’ll be rackt first, Mum budget,—prithee present me.
1686		Behn Lucky Chance V vii: Mum! No words on’t.
c.1698		B.E. Dict. Canting Crew n.p.: Mum-for-that not a Word of the Pudding.
1702		Vanbrugh False Friend Act I: Mum; here’s her Father.
1725		New Canting Dict. [as cit. c.1698].
1737, 1759, 1760, 1776		Bailey Universal Etym. Eng. Dict. [as cit. c.1698].
1754		Foote Knights in Works (1799) I 66: Hush! here’s Mr Jenkins and son Tim. Mum!
1764		K. O’Hara Midas II i: Mum – snugs the word.
1785		‘Peter Pindar’ ‘Lyric Odes’ Works (1794) I 103: But mum!
a.1796		‘While Prose-Work and Rhymes’ in Burns Merry Muses of Caledonia (1965) 57: The Process – but mum – we’ll allow / Poor Justice has ever / For Cunt had a favor.
1800		T. Dibdin Jew and the Doctor II i: Mum, you sly dog!
1811		J. Poole Hamlet Travestie III iv: But mum! here come King, Queen, and all the court.
1823		Egan Grose’s Classical Dict. of the Vulgar Tongue.
1838		W. Holloway Dict. of Provincialisms 114/1: Mum! An exclamation calling for silence.
1842		C. Mathews Career of Puffer Hopkins 113: Breathing the word ‘mum’ in an undertone, and shaking his head in reproof [...] Puffer descended into the yard.
1859		G.H. Miles Mary’s Birthday II i: Remember, mum! It will leak out in good time. Remember mum!
1900		‘Doss Chiderdoss’ ‘A Wordless Play’ Sporting Times 10 Nov. 1/4: A finger to his lips he brought / And mutely signalled ‘Mum!’.

In exclamations

mum your dubber! [dubber n.² ]

be quiet! shut up!

1789		implied at dubber-mum(m)ed under dubber n.2
1860		Hotten Dict. of Modern Sl. etc. (2nd edn) 134: DUBBER, the mouth; ‘mum your dubber,’ hold your tongue.