Unlike hogwash or, for example, flapdoodle, the noun balderdash is a word of “uncertain” (some authorities even say of “unknown”) origin. However, what is “known” about it is probably sufficient for questioning the disparaging epithets.
As often in such cases, it remains unclear whether the word under discussion is native or borrowed. The difficulty with balderdash is that its earliest recorded senses are “froth” and “mixture of drinks.” “Nonsense” and “vile, insulting language” are seemingly later developments, because it is more natural for a word denoting “froth” to acquire figurative meanings (“cheap drink,” “trash,” “nonsense”) than for a word meaning “nonsense” to be applied to a drink. Not that such a change is impossible (puzzling sematic leaps occur all the time); it is only less probable. Compound nouns fit the names of drinks, especially mixed drinks: think of scumgullion and shandygaff. (When the form of a word “corresponds” to its meaning, linguists speak of iconicity. A compound word for a compound drink is the very triumph of iconicity.) Scumgullion is not only tea or coffee made thin but also a kind of stew. Perhaps balderdash too had a wider application one day.
Quite naturally, words for “nonsense” tend to be expressive; funny, partly meaningless compounds, native and borrowed, like claptrap, poppycock, and codswallop are cast ideally for this role. But how was balderdash coined? The Oxford Dictionary of English Etymology says: “Various continental forms f[or] balder– expressing loud noise or clatter are not relevant in sense.” This verdict may be too harsh. The element –dash, which everybody identifies with the verb dash, suggests that producing the mixture was associated with a vigorous, abrupt, or hasty movement: one threw, rather than poured, the ingredients into a bowl, and conceivably did it with some noise, amplified in the word’s form by humor.
Balderdash seems to be a compound of the same type as slapdash or slapjack, or puffball, except that Engl. balder “knock, bang, crash, pop” has not been attested Continental words resembling balder– and meaning “bawl; talk nonsense” are numerous: Norwegian dialectal bjaldra, Dutch balderen ~ German poltern, and so forth. All of them are evidently onomatopoeic.
By Anatoly Liberman, the author of Word Origins & Oxford Etymologist Blog.