The standard dictionary definition — senseless talk or writing; nonsense — may seem anodyne, lacking the fire and passion that so often comes attached to the word. It’s often reserved for circumstances in which common-or-garden invective would be thought inadequate.
This has been so for two centuries. Here is the grandly-named Victorian historian Thomas Babington Macaulay, writing in a footnote in his History of England from James II: “I am almost ashamed to quote such nauseous balderdash”. One of the great wielders of balderdash — it seems somehow to be akin to a bludgeon — was the American journalist H L Mencken; he was in fine form castigating “the general run of business and professional men” in his book In Defense of Women: “Their very capacity to master and retain such balderdash as constitutes their stock in trade is proof of their inferior mentality”.
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”.