An Etymological Dictionary of Astronomy and Astrophysics

“From the beginning,” as opposed to in medias res “starting in the middle of the story.” In physics and chemistry “from first principles;” → ab initio calculation.

Etymology (EN): L. “from the beginning,” from ab “from,” → ab- + initio, ablative of initium “a beginning, an entrance,” from inire “to go into, begin,” from in- “into, in” + ire “to go” (cf. Gk. ienai “to go,” Skt. eti “goes,” O.Pers. aitiy “goes,” Av. aeiti “goes,” Mod.Pers. âyad “comes,” PIE *ei- “to go, to walk”).

Etymology (PE): Hac bon, from Mid.Pers. hac “from” (O.Pers. hacā “from,” Av. hacā “from, out of,” cf. Skt. sácā “with,” PIE base *sek^w- “to follow,” Av. hac-, hax- “to follow,” hacaiti “follows,” Skt. sácate “accompanies, follows,” Gk. hepesthai “to follow,” L. sequi “to follow,” Lith. seku “to follow”)

• bon “beginning, base, root” (Av. būna- “base, depth,” cf. Skt. bundha-, budhná- “base, bottom,” Pali bunda- “root of tree”).