PIE base ‘now, present time’, related to *newo- ‘new’.
Root of only now in English, but widespread in Germanic languages, from Proto-Germanic *nu, well known as a top-level domain name on the Internet: .nu. Also root of Greek nu ‘now, then’, Latin nunc ‘now’, as in Nunc dimittis, and Sanskrit nu ‘now’.
[Pokorny *nū̆- p. 770.]