Etymology
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mote (n.)

"small particle, as of dust visible in a ray of sunlight," Old English mot, of unknown origin; perhaps related to Dutch mot "dust from turf, sawdust, grit," Norwegian mutt "speck, mote, splinter, chip." Hence, anything very small. Many references are to Matthew vii.3.

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radioactive (adj.)

1898, of an atomic nucleus, "capable of spontaneous nuclear decay releasing ionizing emissions," from French radio-actif, coined by Pierre and Marie Curie from radio-, combining form of Latin radius "ray" (see radius) + actif "active" (see active). Of processes, etc., "involving or produced by radioactivity," by 1903.

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radium (n.)

radioactive metallic alkaline earth element, 1899, from French radium, formed in Modern Latin from Latin radius "ray" (see radius). With metallic element ending -ium. Named 1898 after identification by Marie Curie and her husband; so called for its power of emitting energy in the form of rays.

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rad (n.)

1918, "x-ray dose unit," a shortened form of radiation (q.v.). The meaning "unit of absorbed dose of ionizing radiation" is by 1954, an acronym from radiation absorbed dose. As shortened form of radical (n.), it is attested in political slang from 1820. Teen slang adjectival sense of "extraordinary, wonderful" is from late 1970s (see radical (adj.)).

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radial (adj.)

c. 1400, "of or like a ray or radius," from Medieval Latin radialis, from Latin radius "shaft, rod; spoke of a wheel; beam of light" (see radius). Meaning "arranged like the radii of a circle" is by 1750. As a noun, "a radiating or radial part," by 1872. As a type of tire, attested from 1965, short for radial-ply (tire), so called because the cords run at right angles to the circumference. Related: Radially.

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skate (n.1)

"type of flat, cartilaginous fish, a kind of ray," mid-14c., scate, in reference to the common European skate, from a Scandinavian source such as Old Norse skata "skate," Danish skade, Faeroese skøta, a word of unknown origin.

All skates are rays, but all rays are not called skates, this name being applied chiefly to certain small rays of the restricted genus Raia, of both Europe and America. [Century Dictionary]


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tube (n.)

1610s, from French tube (15c.), from Latin tubus "tube, pipe," a word of unknown origin. The London subway was christened the Twopenny Tube by 1900 (H.D. Browne, in the "Londoner" of June 30); tube for "cylindrical railway tunnel" is attested from 1847. The meaning "TV as a medium" is from 1959, short for cathode ray tube or picture tube. Tube top as a women's clothing style is attested from 1972. Tube steak is attested from 1963 as "frankfurter," slang meaning "penis" is recorded by mid-1980s.

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rayon (n.)

type of manufactured fiber, 1924, chosen by National Retail Dry Goods Association of America, probably from French rayon "beam of light, ray," from rai (see ray (n.1)) and so called because it is shiny. A marketer's alternative to the original patented name, artificial silk (1884) and the other marketing attempt, Glos, which was "killed by ridicule" [Draper's Record, June 14, 1924].

[T]he production of rayon in American plants, which in 1920 had been only eight million pounds, had by 1925 reached fifty-three million pounds. The flesh-colored stocking became as standard as the short skirt. ... No longer were silk stockings the mark of the rich; as the wife of a workingman with a total family income of $1,638 a year told the authors of Middletown, "No girl can wear cotton stockings to high school. Even in winter my children wear silk stockings with lisle or imitations underneath." [Frederick Lewis Allen, "Only Yesterday," 1931]

By coincidence, Old French rayon had been borrowed into Middle English centuries earlier as a name for a type of cloth.

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sea monkey (n.)

1909 as a heraldic animal, 1964 as a U.S. proprietary name for brine shrimp (Artemia salina), which had been raised as food for aquarium fish but were marketed as pets by U.S. inventor Harold von Braunhut (1926-2003), who also invented "X-Ray Specs" and popularized pet hermit crabs. He began marketing them in comic book advertisements in 1960 as "Instant Life," and changed the name to Sea Monkeys in 1964, so called for their long tails.

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radius (n.)

1590s, "cross-shaft, straight rod or bar," from Latin radius "staff, stake, rod; spoke of a wheel; ray of light, beam of light; radius of a circle," a word of unknown origin. Perhaps related to radix "root," but de Vaan finds that "unlikely." The classical plural is radii

The geometric sense of "straight line drawn from the center of a circle to the circumference" is recorded from 1650s. Meaning "circular area of defined distance around some place" is attested from 1853. As the name of the shorter of the two bones of the forearm from 1610s in English (the Latin word had been used thus by the Romans).

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