1650s in biology, "having or resembling a tendril;" 1815 in meteorology, from Latin cirrus "lock of hair, tendril" (see cirrus) + -ous. Also sometimes cirrose.

"thick, low, dark cloud from which rain or snow falls," 1932 (earlier use from late 19c. refers to different cloud types), from Modern Latin nimbus "cloud" (see nimbus) + connecting element -o- + stratus (see stratus). Nimbus as "a rain cloud" is attested from 1803. 

"a small cloud," 1788, from cloud (n.) + diminutive suffix -let.

Proto-Indo-European root meaning "cloud."

It forms all or part of: nebula; nebular; nebulosity; nebulous; Neptune; Nibelungenlied; Niflheim; nimbus.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit nabhas- "vapor, cloud, mists, fog, sky;" Greek nephele, nephos "cloud;" Latin nebula "mist, vapor, fog, smoke, exhalation;" German Nebel "fog;" Old English nifol "dark, gloomy;" Welsh niwl "cloud, fog;" Slavic nebo.

1852, from cloud (n.) + scape (n.1).

1590s, from un- (1) "not" + past participle of cloud (v.).

Indonesian name for New Guinea, said to mean literally "cloud-covered."

"without clouds, unobscured," 1590s, from cloud (n.) + -less. Related: Cloudlessly; cloudlessness.

a "bright side" which proverbially accompanies even the darkest trouble; by 1843, apparently from oft-quoted lines from Milton's "Comus," where the silver lining is the light of the moon shining from behind the cloud.

Was I deceived? or did a sable cloud

Turn forth her silver lining on the night?

I did not err, there does a sable cloud,

Turn out her silver lining on the night

And casts a gleam over this tufted grove.

Thomas Warton added the commentary: "When all succour ſeems to be lost, Heaven unexpectedly presents the ſilver lining oſ a ſable cloud to the virtuous."