“cloud (n.)
Old English clud “mass of rock, hill,” related to clod. Metaphoric extension to “raincloud, mass of evaporated water in the sky” is attested by c. 1200 based on similarity of cumulus clouds and rock masses. The usual Old English word for “cloud” was weolcan. In Middle English, skie also originally meant “cloud.”
The four fundamental types of cloud classification (cirrus, cumulus, stratus, nimbus) were proposed by British amateur meteorologist Luke Howard (1772-1864) in 1802. Figuratively, as something that casts a shadow, from early 15c.; hence under a cloud (c. 1500). In the clouds “removed from earthly things; obscure, fanciful, unreal” is from 1640s. Cloud-compeller translates (poetically) Greek nephelegereta, a Homeric epithet of Zeus” (1).
While vapour trails, or contrails, are also clouds, they are not accounted for in Howard’s cloud classification. This is hardly surprising, the first powered aircraft did not take to the skies until 1884 with the advent of the airship. However, despite their increase in frequency with the development of winged aircraft and commercial airlines to become one of the common kinds of cloud worldwide, their type has not been appended to this system of classification, with the exception of sometimes being referred to as ‘cirrus aviaticus’.
While some of them can persist, growing in size to up to several miles in width, you never get rain from even the largest of vapour trails.
(1) Online Etymology dictionary
http://www.etymonline.com/index.php?term=cloud









