*shrug* I dunno, just the way it's said around where I'm at. I guess break apart the a and the o, you have NA and OMI. I say NA either naw or nay. naw-omi is almost impossible to say with my accent. So it's NA (nay)-Omi (oh-mee).
I guess people around this area really don't know or care about linguistics. Plus, there was an old television show in the 60's and one of the characters was
Naomi pronounced NAAAY-omi, extreme emphasis on the Nay.