The Dentals + w in Italic

The change of initial dw - to b - is generally acknowledged for Latin but not for the dialects. The material on hand is not sufficient, however, to prove that the treatment was different in the dialects. The apparent exceptions, and these occur in Latin as well, are due in part to analogy and in part to the fact that dw - is simplified to d - when the following vowel precedes a labial (m, p, b, v) or the next syllable contains w (v). The change of dw - to b - is without doubt the result of assimilation : dҍ-, db-, bb-, b-. Between vowels the d disappears: suāvis, sēvocāre (Brugmann, Gr. I 2 322). This loss must have occurred at a time when the syllabic division was *suād-vis. In the same way we may explain mollis from *mol(d)wis, and derbiōsus from *der(d)wi - with vulgar Lat. b for v. This loss of d was much earlier than the change of dw to b. Hence *londhwos through the comparatively late * londvos became lumbus.