Stress is on the penultimate syllable in Welsh names, so this is NEH-riss, not neh-RISS. Stronger Welsh accents will say it more like NAIR-iss. [ˈnɛr.ɪs] [noted -ed]
Nerys is pronounced NE-riss in Wales, with accent on the first syllable, rolled r, and a short i, as in Harris.Nerys Hughes is a Welsh actress, born in 1941.