Etymology
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jillion (n.)

by 1939, arbitrary coinage, modeled on million, etc. Compare zillion, gazillion.

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zillion (n.)

1942, arbitrary coinage with no definite numerical value; first recorded in Billboard magazine. Compare jillion, gazillion.

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Piggly-Wiggly 
chain of self-service grocery stores, started 1916 in Memphis, Tennessee. According to founder's reminiscence from 1921, an arbitrary coinage, simply "something different from anything used before" ["Current Opinion"].
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Kodak 
brand of hand-held camera, arbitrary coinage by U.S. inventor George Eastman (1854-1932), U.S. trademark registered Sept. 4, 1888. In 1890s, practically synonymous with camera and also used as a verb (1891). Kodachrome, registered trademark for a method of color photography, 1915; the product was discontinued in 2006.
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Pyrex (n.)

1915, proprietary name (Corning Glass Works, Corning, N.Y.) of a type of hard, heat-resistant glass, an arbitrary coinage, in which advertisement writers and eager etymologists see implications of Greek pyr "fire" and perhaps Latin rex "king;" but the prosaic inventors say it was based on pie (n.1), because pie dishes were among the first products made from it. The -r-, in that case, is purely euphonious.

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sylph (n.)

1650s, "air-spirit," from Modern Latin sylphes (plural), coined 16c. by Paracelsus, originally referring to any race of spirits inhabiting the air, described as being mortal but lacking a soul. Paracelsus' word seems to be an arbitrary coinage, but perhaps it holds a suggestion of Latin silva and Greek nymph, or Greek silphe "a kind of beetle," but French etymologists propose a Gaulish origin.

The Century Dictionary comments that, "to occultists and quacks like Paracelsus words spelled with -y- look more Greek and convincing." The idea itself seem to have come from the air-spirits of Cabbalism. The meaning "graceful girl" is recorded by 1838, on the notion of "slender figure and light, airy movement" [OED].

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