An Etymological Dictionary of Astronomy and Astrophysics

1. Guided by truth, reason, justice, and fairness.
   

2. Done or made according to principle; equitable; proper.
   

3. Based on right; rightful; lawful (Dictionary.com).

Etymology (EN): M.E. juste, from O.Fr. juste “just, righteous,” from L. iustus “upright, equitable,” from ius “right,” especially “legal right, law,” from O.L. ious, perhaps literally “sacred formula.”

Etymology (PE): Dâdmand, from dâd “law, → justice.”
Râst, → right.
Dorost “whole, complete, right,” → integral.