Nu: Interjection: Well; so.
Noun: The 13th letter of the Greek alphabet.
For interjection: From Yiddish nu, of imitative origin. Earliest documented use: 1892.
For noun: From Greek nu. Earliest documented use: 1425.
“And nu, what happier ending is there than that?”
Nathaniel Rich; Save Us; The New York Times Book Review; Sep 30, 2012.