butterfly (n.)youdaoicibaDictYouDict
Old English buttorfleoge, evidently butter (n.) + fly (n.), but of obscure signification. Perhaps based on the old notion that the insects (or witches disguised as butterflies) consume butter or milk that is left uncovered. Or, less creatively, simply because the pale yellow color of many species' wings suggests the color of butter. Another theory connects it to the color of the insect's excrement, based on Dutch cognate boterschijte. An overview of words for "butterfly" in various languages can be found here. Also see papillon.

Applied to persons from c. 1600, originally in reference to vain and gaudy attire; by 1806 in reference to transformation from early lowly state; in reference to flitting tendencies by 1873. The swimming stroke so called from 1936. Butterflies "light stomach spasms caused by anxiety" is from 1908.
The butterfly effect is a deceptively simple insight extracted from a complex modern field. As a low-profile assistant professor in MIT's department of meteorology in 1961, [Edward] Lorenz created an early computer program to simulate weather. One day he changed one of a dozen numbers representing atmospheric conditions, from .506127 to .506. That tiny alteration utterly transformed his long-term forecast, a point Lorenz amplified in his 1972 paper, "Predictability: Does the Flap of a Butterfly's Wings in Brazil Set Off a Tornado in Texas?" [Peter Dizikes, "The Meaning of the Butterfly," The Boston Globe, June 8, 2008]
extrapolation (n.)youdaoicibaDictYouDict
1867, noun of action from extrapolate by analogy of interpolation; original sense was "an inserting of intermediate terms in a mathematical series." Transferred sense of "drawing of a conclusion about the future based on present tendencies" is from 1889.
reactionary (adj.)youdaoicibaDictYouDict
1831, on model of French réactionnaire (19c.), from réaction (see reaction). In Marxist use, "tending toward reversing existing tendencies," opposed to revolutionary and used opprobriously in reference to opponents of communism, by 1858. As a noun, "person considered reactionary," especially in politics, one who seeks to check or undo political action, by 1855.
skipjack (n.)youdaoicibaDictYouDict
1550s, "a pert shallow-brained fellow; a puppy, a whipper-snapper; a conceited fop or dandy" [OED], from skip (v.) + generic name jack (n.). Applied 1703 to tropical fishes with leaping tendencies. In reference to a kind of sailing boat used on Chesapeake Bay, attested from 1887.
tendential (adj.)youdaoicibaDictYouDict
1877, from Latin stem of tendency + -al (1). Related: Tendentially.
Tendenziöse is a term that has become very common in Germany to describe the Tübingen criticism, and has arisen from the lengths to which theologians of this school have shown themselves ready to go, to establish the hypothesis that the New Testament writings arose out of conflicting tendencies in the early church and efforts to bring about compromises between these factions. The word has been transferred in the translation under the form "tendential." [translator's preface to "Hermeneutics of the New Testament" by Dr. Abraham Immer, translated by Albert H. Newman, 1877]
wasp (n.)youdaoicibaDictYouDict
Old English wæps, wæsp "wasp," altered (probably by influence of Latin vespa) from Proto-Germanic *wabis- (cognates: Old Saxon waspa, Middle Dutch wespe, Dutch wesp, Old High German wafsa, German Wespe, Danish hveps), from PIE *wopsa-/*wospa- "wasp" (cognates: Latin vespa, Lithuanian vapsa, Old Church Slavonic vosa "wasp," Old Irish foich "drone"), perhaps from *webh- "weave" (see weave (v.)). If that is the correct derivation, the insect would be so called for the shape of its nest. Of persons with wasp-like tendencies, from c. 1500. Wasp-waist in reference to women's figures is recorded from 1870 (wasp-waisted is from 1775).