balderdash [bawl-der-dash ]
1. Senseless, stupid, or exaggerated talk or writing; nonsense.
2. (obsolete) A muddled mixture of liquors.
Such unscientific balderdash," added the doctor, flushing suddenly purple, "would have estranged Damon and Pythias." (Robert Louis Stevenson, Dr Jekyll and Mr Hyde)
Then there’s Donald Glover, king of all media, who takes on the role of Lando, Han’s old frenemy, and offers a take on the character that suggests so much of his effortless cool is bluster and balderdash. 5 things to know about Solo: A Star Wars Story, Vix, May 2018)
And I think this is just the most unadulterated balderdash, the most mindless drivel. (Are Sci-Fi Movies Getting Too Pretentious?, Wired, Sep 2019)
1590s, of obscure origin despite much 19c. conjecture; in early use 'a jumbled mix of liquors' (milk and beer, beer and wine, etc); by 1670s as 'senseless jumble of words.' Perhaps from dash and the first element perhaps cognate with Danish balder 'noise, clatter' (see boulder). But the word may be merely one of the numerous popular formations of no definite elements, so freely made in the Elizabethan period. (Online Etymological Dictionary)
It's a pity that such a fine word should come of unknown stock, but we really don't have a clear idea where it comes from. Some argue its origin lies in the Welsh baldorddus, idle noisy talk or chatter (though that is pronounced very differently), while others point to related words in Dutch, Icelandic and Norwegian, such as the Dutch balderen, to roar or thunder. It appears around the time of Shakespeare with the meaning of froth or frothy liquid, or a jumbled mixture of liquids, such as milk and beer, or beer and wine. Only in the latter part of the seventeenth century did it move towards its modern meaning, through the idea of speech or writing that is a senseless jumble, hence nonsense or trash.
It has also been used as a verb, meaning to make a jumbled mixture of ingredients or, in plain English, to adulterate. Tobias Smollett used it in his Travels through France and Italy in 1766 to refer to French wine: "That which is made by the peasants, both red and white, is generally genuine: but the wine-merchants of Nice brew and balderdash, and even mix it with pigeons' dung and quick-lime." (World Wide Words)