Etymology
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fission (n.)
1819, "division of a cell or organism," from Latin fissionem (nominative fissio) "a breaking up, cleaving," from past participle stem of findere "to split" (from PIE root *bheid- "to split"). Cognate with Old English bitan "to bite." Nuclear physics sense is 1939. As a verb, from 1929.
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*bheid- 
Proto-Indo-European root meaning "to split," with derivatives in Germanic "referring to biting (hence also to eating and to hunting) and woodworking" [Watkins].

It forms all or part of: abet; bait (n.) "food used to attract prey;" bait (v.) "to torment, persecute;" bateau; beetle (n.1) "type of insect; bit (n.1) "small piece;" bite; bitter; bitter end; boat; boatswain; -fid; fissile; fission; fissure; giblets; pita; pizza; vent (n.).

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit bhinadmi "I cleave," Latin Latin findere "to split, cleave, separate, divide," Old High German bizzan "to bite," Old English bita "a piece bitten off, morsel," Old Norse beita "to hunt with dogs," beita "pasture, food."
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monogony (n.)

"asexual reproduction, reproduction by fission or gemmation," 1869, from Greek monos "single, alone" (see mono-) + -gonia "a begetting," from gonos "birth" (from PIE root *gene- "give birth, beget"). 

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promethium (n.)

radioactive element, long one of the "missing elements," 1948, so called by discoverers Jacob Marinsky and Lawrence Glendenin, who detected it in 1945 in the fusion products of uranium while working on the Manhattan Project. From Prometheus (q.v.), who stole fire from the gods and was punished for it, + element name ending -ium. "The name not only symbolizes the dramatic way in which the element may be produced in quantity as a result of man's harnessing of the energy of nuclear fission, but also warns man of the impending danger of punishment by the vulture of war." [Marinsky and Glendenin]

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