Etymology: Middle English bernak , < Old French bernac ‘camus’; of which bernacle seems to be a diminutive form: compare Old French bernicles in Joinville c1275, in sense of the instrument of torture (sense 2) as used by the Saracens, for which Marsh has suggested an eastern origin, comparing Persian baran-dan to compress, squeeze, baranjah kar-dan to inflict torture. But, so far as evidence goes, 1 was the earliest sense, and of western origin. The sense of ‘spectacles’ seems to arise naturally enough from the others, but has been treated by some as distinct, and referred to Old French béricle (since 15th cent. bésicle) ‘eye glass,’ originally ‘beryl’ < late Latin *bericulus, diminutive of berillus, beryllus: it is not easy to trace any phonetic connection between this and barnacles, even though the modern French dialect of Berry has berniques ‘spectacles.’

Etymology: Middle English bernekke, bernake, identical with Old French bernaque, medieval Latin bernaca, berneka. (Other French forms bernache, barnache; Portuguese bernaca, -acha, -icha, Spanish bernache; medieval Latin also barnaces, bernesta, barneta, perhaps bad spellings). With the β forms compare medieval or modern Latin bernicla, -ecela, -acula, and modern French bernicle, barnacle. Ulterior history unknown. The earliest attainable forms (omitting barbates in Albertus Magnus and barliates in Vincentius Bellovacensis, which seem too far off) are the English bernekke , Anglo-Latin bernaca (Giraldus Cambr. c1175), barneta , ? barneca (Gervase of Tilbury c1211), berneka (Vincent. Bellovac. 1200–1250). If English, this could only be bare-neck or bear-neck , of which the application is not evident. The history of this word is involved in an extraordinary growth of popular mythology, traced back as far as the 11th or 12th centuries by Prof. Max Müller, Lect. Sc. Lang. (ed. 7) II. 583–604. It is there suggested that bernacula might be a variant of *pernacula , a possible diminutive of perna ‘a kind of shellfish,’ afterwards confused with *bernicula , a supposed aphetic form of *hibernicula , which might be applied to the barnacle-goose from its being found in Hibernia . Others seek the source of the primitive bernaca in Celtic, comparing Gaelic bairneach , Welsh brenig , limpets. But as all the evidence shows that the name was originally applied to the bird which had the marvellous origin, not to the shell which, according to some, produced it, conjectures assuming the contrary seem to be beside the mark. The form bernacle , it will be seen, is not found before 15th cent., and bernacula seems to be only its modern Latin adaptation. If medieval Latin bernecla , bernicla , are earlier, they may be errors for bernecha , bernicha . No connection with barnacle n.¹ can be traced: bernac was masculine, bernaque, -ache (feminine), in French.

Etymology: < barnacle n.¹Previous versions of the OED give the stress as: ˈbarnacle.

Etymology: < barnacle n.²