נָא

English (Strong)

a primitive particle of incitement and entreaty, which may usually be rendered: "I pray," "now," or "then"; added mostly to verbs (in the Imperative or Future), or to interjections, occasionally to an adverb or conjunction: I beseech (pray) thee (you), go to, now, oh.
apparently from נוּא in the sense of harshness from refusal; properly, tough, i.e. uncooked (flesh): raw.