in reference to a hypothetical cloud of small objects beyond Pluto that become comets, proposed 1949 by Dutch astronomer Jan Hendrick Oort (1900-1992), and named for him by 1968.
late 14c., "Roman god of the sea," from Latin Neptunus, the Roman god of the sea (son of Saturn, brother of Jupiter, later identified with Greek Poseidon), probably from PIE root *nebh- "cloud" (source of Latin nebula "fog, mist, cloud"), via a sense of "moist, wet."
The planet so named was discovered by German astronomer Johann Gottfried Galle (1812-1910) on the night of Sept. 23-24, 1846 and named by French astronomer Urbain Le Verrier (1811-1877), who had predicted its position based on anomalies in the motion of Uranus and sent the coordinates to Galle. It is too dim to be seen with the naked eye, but it had been seen by observers using telescopes as far back as Galileo, but they did not recognize and identify it as a planet. Until the identification of Pluto in 1930 (and since that planet's demotion), it was the most distant known planet of the solar system.
loose ("open") star cluster (M44) in Cancer, 1650s, from Latin praesaepe the Roman name for the grouping, literally "enclosure, stall, manger, hive," from prae "before" (see pre-) + saepire "to fence" (see septum).
It is similar to the Hyades but more distant, about 600 light-years away (as opposed to about 150 for the Hyades), consists of about 1,000 stars, mostly older, the brightest of them around magnitude 6.5 and thus not discernible to the naked eye even on the clearest nights, but their collective light makes a visible fuzz of nebular glow that the ancients likened to a cloud (the original nebula); Galileo was the first to resolve it into stars (1609).
The modern name for it in U.S. and Britain, Beehive, seems no older than 1840. Greek names included Nephelion "Little Cloud" and Akhlys "Little Mist." "In astrology, like all clusters, it threatened mischief and blindness" [Richard Hinckley Allen, "Star Names and Their Meanings," 1899].
"Manger" to the Romans perhaps by influence of two nearby stars, Gamma and Delta Cancri, dim and unspectacular but both for some reason figuring largely in ancient astrology and weather forecasting, and known as "the Asses" (Latin Aselli), supposedly those of Silenus.
"of or pertaining to Portuguese navigator Fernão de Magalhães (c. 1470-1521), the first European to round the tip of South America, whose surname was Englished as Magellan.
The Magellanic Clouds, the two cloud-like patches of stars in the southern heavens, are attested under that name by 1680s. Magellan described them c. 1520, hence the name in Europe; but at least the larger of the two had been mentioned in 1515 by Peter Martyr d'Anghiera, chronicler of explorations in Central and South America.
In English they were earlier the Cape Clouds, because they became prominent as sailors rounding Africa neared the Cape of Good Hope; "but after Magellan became noted and fully described them they took and have retained his name." [Richard Hinckley Allen, "Star Names and Their Meanings," 1899]
Coompasinge abowte the poynt thereof, they myght see throughowte al the heaven about the same, certeyne shynynge whyte cloudes here and there amonge the starres, like unto theym whiche are scene in the tracte of heaven cauled Lactea via, that is the mylke whyte waye. [Richard Eden, translation of "Decades of the New World," 1555]