On 9 Apr 2017 08:24, "R A Brown" <[log in to unmask]> wrote:

The regular vocative singular was _Dee_ which was used by
Tertullian and Prudentius. But pronouncing this as two
syllables (both Es being short) correctly in normal speech
is clearly awkward.

It was IMO fairly 'natural' for the anonymous
translators of the Old latin versions to use _deus_ rather
than the phonetically awkward _dee_.

I am away from my copy of Vox Latina, so let me ask more about this
awkwardness. Any awkwardness surely can't have been literally purely
phonetic. Assuming that contiguous heterosyllabic (what's the evidence for
the heterosyllabicity?) identical nonhigh vowels were phonologically licit,
perhaps the problem was the combination of their rarity and the marginality
of their phonetic contrast with other long monophthongs? Or maybe they were
phonologically licit in earlier Latin but became illicit along with other
reorganizations to the vowel system? -- I speculate from a position of
ignorance, but a purely phonetic explanation cannot be right.