Note: The modern English outcome with [ʌ] presupposes shortening of (or variation with) a Middle English form with ọ̄, itself presupposing Old English ŭ affected by Middle English open-syllable lengthening. Middle English spellings such as douve, however, would seem to require an Old English long vowel, as do the Germanic cognates. These issues were pointed out by E. J. Dobson (English Pronunciation, 1500-1700, 2. edition, Oxford, 1968, p. 514), who follows the Oxford English Dictionary's suggestion that the noun is related to Old English dūfan "to dive, plunge (into a liquid)" (see dive entry 1) and that the forms with long and short u reflect different ablaut grades of dūfan (a class II strong verb). Essentially the same solution, without the discussion of the English details, is proposed by G. Kroonen (Etymological Dictionary of Proto-Germanic, Brill, 2013). The difficulty with this hypothesis is that the noun in Germanic languages uniformly means "dove, pigeon," not an aquatic bird. Another proposal associates *dūƀōn- with the Celtic etymon of Old Irish dub "dark, black," Old Welsh dub, Welsh du, on the assumption that a dove is "the dark bird." But such a source, usually derived, together with Germanic *dauƀa- "deaf, senseless" (see deaf) and Greek typhlós "blind, dark," from Indo-European *d^hub^h-, *d^heu̯b^h-, could not regularly produce a long u. The Oxford Dictionary of English Etymology, the etymological successor to the Oxford English Dictionary, abandons the dive connection and says simply "presumed to be imitative of the bird's note."