An Etymological Dictionary of Astronomy and Astrophysics

A system of two perpendicular fine threads of wire placed in the focus of the eyepiece of an optical instrument and used as a sighting reference.

Etymology (EN): → cross; → hair.

Etymology (PE): Târbast, from târ + bast. The first component târ “thread, string, wire,” cognate with tanidan, tan- “to spin, twist, weave,” → tension; the second component bast “to bind; to arrange” (past stem of bastan, from Mid.Pers. bastan/vastan “to bind, shut,” → band.