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.
"altar top," 1848, Latin, literally "table," also "meal, supper," and "altar, sacrificial table," hence used in Church Latin for "upper slab of a church altar" (see mesa). With a capital M-, the name of an organization for people of IQs of 148 or more founded in England in 1946, the name chosen, according to the organization, to suggest a "round table" type group. The constellation (1763) originally was Mons Mensae "Table Mountain." It is the faintest constellation in the sky, with no star brighter than magnitude 5.0.
La Caille, who did so much for our knowledge of the southern heavens, formed the figure from stars under the Greater Cloud, between the poles of the equator and the ecliptic, just north of the polar Octans; the title being suggested by the fact that the Table Mountain, back of Cape Town, "which had witnessed his nightly vigils and daily toils," also was frequently capped by a cloud. [Richard Hinckley Allen, "Star Names and Their Meanings," London: 1899]
"weather condition consisting of a cloud resting upon the ground, fog," also "precipitation consisting of fine droplets of water, much smaller than rain," Old English mist (earliest in compounds, such as misthleoðu "misty cliffs," wælmist "mist of death"), from Proto-Germanic *mikhstaz (source also of Middle Low German mist, Dutch mist, Icelandic mistur, Norwegian and Swedish mist), perhaps from PIE *meigh- "to urinate." Greek omikhle "fog;" Old Church Slavonic migla"fog;" Sanskrit mih- "fog, mist," megha "cloud" sometimes are said to be cognates in this secondary sense, but Beekes finds these rather more likely to be from a separate IE root meaning "fog."
Sometimes distinguished from fog, either as being less opaque or as consisting of drops large enough to have a perceptible downward motion. [OED]
Also in Old English in reference to dimness of the eyes or eyesight, either by illness or tears, and in a figurative sense of "something that darkens and obscures mental vision." Meaning "haze of dust in the air producing obscurity of things seen at a distance" is by 1785.
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.
"cloud of bees or other insects," Old English swearm "swarm, multitude," from Proto-Germanic *swarmaz (source also of Old Saxon, Middle Low German swarm, Danish sværm "a swarm," Swedish svärm, Middle Dutch swerm, Old High German swaram, German Schwarm "swarm;" Old Norse svarmr "tumult"), by Watkins, etc., derived from PIE imitative root *swer- "to buzz, whisper" (see susurration) on notion of humming sound, and thus probably originally of bees. But OED suggests possible connection with base of swerve and ground sense of "agitated, confused, or deflected motion." General sense "large, dense throng" is from early 15c.
c. 1300, manacen, "to threaten, express a hostile intention toward," from Old French menacier "to threaten; urge" (11c.), Anglo-French manasser, from Vulgar Latin *minaciare "to threaten," from minacia "menace, threat" (see menace (n.)). Intransitive sense of "to be threatening, pose a threat of danger or harm" (of abstractions or objects) is from mid-14c. Related: Menaced; menacing.
Threaten is of very general application, in both great and little things: as, to be threatened with a cold; a threatening cloud; to threaten an attack along the whole line. Threaten is used with infinitives, especially of action, but menace is not; as, to threaten to come, to punish. Menace belongs to dignified style and matters of moment. [Century Dictionary]
There probably was an Old English cognate but it is not attested in surviving documents. The nasalized form likely is a variant of Old Norse bakki "(river) bank, ridge, mound; cloud bank," cognate with Swedish backe, Danish bakke "hill, rising ground."