Green’s Dictionary of Slang

1. any adulterated or mixed drink, typically milk and beer, beer and wine, brandy and mineral water, which, while duly consumed, was generally considered unpleasant.

[1599		Nashe Praise of the Red Herring 8: They would no more [...] have their heads washt with his bubbly spume or Barbers balderdash].
1629		Jonson New Inn I i: It is against my freehold [...] To drink such balderdash, or bonny-clabber!
1637		J. Taylor Drinke and Welcome 11: Beere, by a Mixture of Wine [...] hath lost both Name and Nature, and is called Balderdash.
1641		T. Heywood Reader, Here You’ll Plainly See Judgement 6: Where sope hath fayl’d without, Balderdash wines within, will worke no doubt.
c.1698		B.E. Dict. Canting Crew.
1766		Smollett Travels through France and Italy 208: The wine merchants of Nice brew and balderdash and even mix it with pigeon’s dung and quicklime.
1785, 1788, 1796		Grose Classical Dict. of the Vulgar Tongue.
1799		Sporting Mag. Mar. XIII 364/1: The vilest compounds, while Balderdash vends, / And brews his dear poison for all his good friends.
1811		Lex. Balatronicum.
1823		Egan Grose’s Classical Dict. of the Vulgar Tongue.

2. used attrib., an innkeeper.

1702

Farquhar Twin-Rivals I i: Take this; pay for a bottle of wine, and bid Balderdash [inn keeper] bring it.

3. obscenity.

1674		Marvell Rehearsal Transpos’d 243: Did ever Divine rattle out such prophane Balderdash!
1777		H. Tooke Trial 38: I had heard him talk against ‘indecency, a flood of obscenity, and scandalous publications.’ [...] he represents me to you in the light of a scurrilous, ribald, balderdash, Billingsgate, impudent fellow.
1791		J. Walker Pronouncing Dict. 42/1: Balderdash, Rude mixture.
1823		Egan Grose’s Classical Dict. of the Vulgar Tongue.
1838		W. Holloway Dict. of Provincialisms 6/2: Balderdash, Filthy; obscene language.

4. sense 1, in fig. use, second-rate, ‘thin’.

1779

Nocturnal Revels 2 214: It [i.e. a poem] was a stupid, insipid, balderdash performance.

5. (Anglo-Irish) a fool.

1821

‘A Real Paddy’ Real Life in Ireland 267: Wasn’t it vexing to be intrapted by such a useless balderdash as him, who has no more occasion for a wife than a cow has for a side-pocket.