James Murray showed great caution in his discussion of the Modern English words spelled and pronounced as brash (see Part I of this essay). It remains unclear how many of them are related. One of the homonyms seems to go back to French, but even that word is of Germanic origin. The entry in the OED online has not yet been revised, and revising it will entail many difficulties.
To begin with, Icelandic also has a word sounding like Engl. brash. It ends in –s, but sh is a late addition to the phonetic inventory of English, so that the mismatch s versus sh is of no consequence. The real problem consists in the fact that the Icelandic word surfaced in print only in the seventeenth century. It means “bad weather; hard work, anxiety; sexual urge.” Its cognates (or seeming cognates!) in other Germanic languages mean “to burn, crackle; to fall down with a noise; arrogant, uncontrollable.” At first sight, the common semantic base of all of them appears to be “great force; impetuosity.” It accords well with Engl. brash “attack, assault,” and “arrogant” is also familiar to us from English. If we are dealing with an old word, unrecorded in Medieval Scandinavian, Engl. brash may, but does not have to be, a borrowing from Norwegian or Danish.
“Burn” appears to be at variance with “noise” and the rest, even though Germanic apparently had the noun brasa, which was borrowed into French and continues as braise “hot coals”; the word is familiar to English speakers from brazier. Burn may be an extension of the sense “spring forth forcibly like a flame”; think of, for instance, Scotch and northern English burn “little stream, rivulet.” And, if we take into account German Brunst “lust; rutting season, heat,” then Icelandic bras “sexual urge” will be a perfect match for it. A rebellious family it is: “noise, passion, fire, assault”! However, we still cannot decide whether we are dealing with a group of Germanic adjectives, nouns, and verbs (the oldest of them being burn, from some form like brennan), represented in several languages, or whether some of them were borrowed from or into Scandinavian.
The Century Dictionary describes the situation in the same terms as the OED. It too points to the fact that the senses overlap and make the separation of brash1, 2, 3, 4 uncertain. Additionally, it states, again exactly like Murray, that similar-sounding words designate all kinds of loud noises and are reminiscent of bash, dash, clash. Several Scandinavian and German verbs beginning with br-are cited. Finally, the obsolete, except as dialectal, Engl. brastle is glossed as “to crack; crackle; boast, brag.” When things are brittle and break, they make a noise. Here then is another possible link. In principle, it would be rather natural to derive all the occurrences of brash from some nuclear meaning “breakable, brittle; hence noisy; crack” and, by extension, even “crackle; burn.” “Rash, impetuous; sexually aroused; attack” would be natural metaphorical senses. It is tempting to follow Jacob Grimm and reconstruct a common “root” of so many divergent forms. But, as I keep repeating, semantic bridges are easy to build, and that is why they tend to collapse at the gentlest push. The history of brash is made particularly obscure because most words pronounced so turned up in written monuments late; besides some of them may be sound-imitative. We have already witnessed two points of departure but need only one.
Most of what has been said above, except for the connection brash—burn, can be found in the first edition of the OED, but there has been another attempt to discover the etymology of brash, in at least one of its senses, and it takes us in a different direction. Rather long ago, English etymologists used to cite the fish name bass as a possible cognate of brash. The Old English for bass was bærs ~ bears. Bass is the product of metathesis: the vowel and r changed places, as they did in burn “stream,” its metathesized doublet bourn (different from Hamlet’s bourne), from brunna-, and in the verb burn, from brenna-. (From burn “stream” comes the family name Burns.) Later, r was lost in the r-less dialects of British English. A similar change occurred in the fish name dace, from French dars (related to Engl. dart). German and Dutch have retained the initial form of the fish name: Barsch and baars respectively. British regional barse (known, for example, in the northwest) is their exact congener. The origin of bass is known. It is a “bristled” fish of the perch family. The root of bristle can also be seen in Borste and Bürste, the German for “bristle” and “brush.” But German (and this is the main point) also has the adjective barsch “harsh, curt, abrupt,” which can hardly be separated from the fish name and from Engl. brash. German Barsch is a northern word, which makes its ties to Engl. barse, bass even more convincing and important. The fish called bass ~ barse got its name from the sharp dorsal fin. Incidentally, Old Icelandic, had barr (that is, bar–r: the second r is an ending) “vigorous,” and it is it is probably related to bras ~ brash ~ Barsch.
Above, I tried to find a common denominator for the concepts ranging from “brittle” to “sexual urge” in “great force, impetuosity” or “noise.” “Sharpness” will do equally well, if not better. It will perhaps be incautious to deny the influence of bash, clash, dash on Engl. brash. Some of its senses may not have arisen if the word had a different phonetic shape. Also, we need not assume that all the present day senses developed at the same time, especially if we again remember how late most of our attestations are. Here I am only pleading for the restitution of the fish name in the entry on brash “attack; rash, impetuous.” Those senses go very well with sharpness. The verb break might have accelerated or even caused the emergence of brash “brittle” and “broken branches.” Burning and sharpness are also good allies. On the whole, it is not too hard to produce an evolutionary line, beginning with the nuclear sense “sharp” (hence the fish name, “attack,” “pain,” “rashness”) to metaphorical senses: “impudent, sexually aroused.” In this scenario, “brittle” refuses to cooperate but can perhaps be forced into this scheme.
The conclusion is obvious. Thanks to the fish name, we seem to know more about the history of brash than our contemporary English dictionaries make us believe. The least attractive lexicographical solution would be to retain the verdict that the many senses of brash are hardly compatible or that the word’s (or words’) origin is unknown. Unknown is a loose concept. One thing is to know nothing about the subject (a possible situation: some words are indeed like aliens: they exist, but their past is beyond reconstruction), and quite a different thing is to have a hypothesis that cannot be proved beyond reasonable doubt but is good enough to stimulate further research. Our great dictionaries are timid, because their users take the verdicts given there for God’s truth. We have to advise people to give up their illusions and state frankly that the much sought-after ultimate truth is rarely achievable in etymology. However, it does not follow that we should hide behind careful, uninformative pronouncements and leave our readers in the dark. We should remain wise and yet attack, assault our target with the brashness of youth and the noisy impetuosity of an ardent lover.
Images: (1) Robert Burns portrait by Alexander Nasmyth, Public Domain via Wikimedia Commons. (2) “Bass” by PublicDomainImages, Public Domain via Pixabay. (3) “The Crown of Love” by John Everett Millais, Public Domain via Wikimedia Commons. Featured image: “Largemouth bass fish art work micropterus salmoides” by Raver Duane, U.S. Fish and Wildlife Service, Public Domain via Wikimedia Commons.