Probably of Persian origin; an epistle -- letter.
H5406. nishtevan
נִשְׁתְּוָן noun [masculine] letter (usually derived from Persian , i.e. writing, HoffmZA ii (1887), 52 yet compare MeyerJudenthum 22); — absolute ׳נ Ezra 4:7; 7:11.
נתב (√ of following; Arabic swell forth, become prominent, protuberant, Lane2760).