An Etymological Dictionary of Astronomy and Astrophysics

1. To show (a claim, statement, act, etc.) to be right, reasonable, or proper.
   
2. To defend or uphold as warranted or well-grounded.
   
3. To adjust (a line of type) to fill a line of constant width.

Etymology (EN): Justify, from O.Fr. justifier “to show (something) to be just or right; to administer justice,” from L. justificare “act justly toward, make just,” from justificus “dealing justly, righteous,” from justus “just, upright, equitable,” from jus (gen. juris) “right,” from O.Latin ious, from PIE base *yewes- (cf. Av. yaož-da- “to purify ritually, to revitalize;” Skt. yos- “(long) life” + root of facere “to do” (from PIE base *dhe- “to put, to do;” cf. Mod.Pers. dâdan “to give;” O.Pers./Av. dā- “to give, grant, yield,” dadāiti “he gives; puts;” Skt. dadáti “puts, places;” Hitt. dai- “to place;” Gk. tithenai “to put, set, place;” Lith. deti “to put;” Czech diti, Pol. dziac’, Rus. det’ “to hide,” delat’ “to do;” O.H.G. tuon, Ger. tun, O.E. don “to do”).

Etymology (PE): Râstâvard kardan, râstâvardan, infinitives of râstâvard,
→ justification.