An Etymological Dictionary of Astronomy and Astrophysics

1. The act or process of splitting or breaking into parts.
   

2. Splitting of the nucleus of an atom into two or more fragments of comparable size, usually as the result of the impact of a neutron on the nucleus. Same as → nuclear fission.

Etymology (EN): Fission, from L. fissionem “a breaking up, cleaving,” from root of findere “to split.”

Etymology (PE): Šekâft, stem of šekâftan “to split, break, tear,” akin to kaftan, kâftan “to split; to dig,” Parthian Mid.Pers. q’f- “to split;” Sogdian kβ “to split;” Chorasmian kf- “to split, be split;” Proto-Iranian *kap-, *kaf- “to split.”