An Etymological Dictionary of Astronomy and Astrophysics

The action of rapidly moving a telescope in the alpha or delta direction under computer control as it moves to point at a new position in the sky.

Etymology (EN): Slew “to turn, swing, twist,” earlier slue a nautical word, of unknown origin.

Etymology (PE): Tondrâneš, literally “driving fast,” from tond “swift, rapid, brisk; fierce, severe” (Mid.Pers. tund “sharp, violent;” Sogdian tund “violent;” cf. Skt. tod- “to thrust, give a push,” tudáti “he thrusts;” L. tundere “to thrust, to hit” (Fr. percer, E. pierce, ultimately from L. pertusus, from p.p. of pertundere “to thrust or bore through,” from per- + tundere, as explained); PIE base *(s)teud- “to thrust, to beat”) + râneš, verbal noun of rândan “to push, drive, cause to go,”
causative of raftan “to go, walk, proceed” (present tense stem row-, Mid.Pers. raftan, raw-, Proto-Iranian *rab/f- “to go; to attack”).