Brychan wrote:I think that ac/nac instead of ag/nag is just a spelling convention that is at odds with the actual pronunciation.
There are, if I remember correctly, a lot of spellings like that in Old Welsh or Middle Welsh (which led some people to believe that Southern hardening was a conservatism); I'm not sure whether this one is, though, since it causes mixed mutation which historically was caused by a cluster of /t p k/ + a consonant (so
nid for example was apparently originally
nit, and so on, with a very early voicing of post-vowel consonants).
Although actually, that post-vocalic lenition happened very early in Welsh, so it's possible that it was 'nac' before Welsh was ever written down and pronounced 'nag' even in Old Welsh despite a conservative spelling with <c>.
Anyway, I've never heard anything but 'nag' for written
nac and even in school we were taught to pronounce it that way (which is amazing since if there's anywhere obsessed with spelling pronunciations it is the second-language school system).