Green’s Dictionary of Slang

hugger-mugger n.¹

In phrases

in hugger-mugger (adv.) [SE hugger-mugger, concealment, secrecy]

secretly, clandestinely.

1523		Skelton Colyn Cloute (1550) Aiii: Alas they make me shoder For in hoder moder The churche is put in faute.
1542		Udall (trans.) Erasmus’ Apophthegms (1564) Bk II 240: Why wouldst thou auoide to haue al the worlde priuie to it [...] to be done secretly in hugger mugger?
1555		J. Philpot in Coverdale Letters of Marytyrs (1838) 178: They would indeed condemn you in hugger-mugger.
1577		Misogonus in Farmer (1906) III ii: This has been kept in hugger-mugger a good while.
1589		Lyly Pappe with an Hatchet B2: He woulde not smoother vp sinne, and deale in hugger mugger against his Conscience.
1593		G. Harvey Pierce’s Supererogation 134: [He] said he would not smoother-vp sinne, and deale in hugger-mugger against his conscience.
1600		J. Day Blind Beggar of Bednall-Green Act IV: I do but stay here to talk 3 or 4 cold words in hugger-mugger with the Blind-beggars Daughter.
1613		Dekker A Strange Horse-Race in Grosart Works (1885) 353: What I giue to them shall bee in Hugger-Mugger.
1621		Middleton Anything for a Quiet Life I i: Such a day I lost fifty pound in hugger mugger at dice.
1633		Ford ’Tis Pity She’s a Whore III i: There’s no way but to clap up a marriage in hugger-mugger.
1669		R. L’Estrange Fables of Aesop CLVI 141: Let the Reproche be never so True, it can hardly be Honest, Where the Office is done in Hugger-Mugger.
1700		‘The Art of Drinking’ Wit’s Cabinet 136: He that Drinks in hugger-mugger, a Bencher.
1796		Grose Classical Dict. of the Vulgar Tongue (3rd edn) n.p.: Hugger Mugger. By stealth, privately, without making an appearance. They spent their money in a hugger mugger way.
1811		Lex. Balatronicum [as cit. 1796].