nebʰ-
“cloud, mist”cloud, sky, mist
Root for cloud/mist, yielding Latin nebula, Greek nephos, German Nebel, Sanskrit nabhas.
Discussion
The Proto-Indo-European root *nebʰ- carried the sense of cloud, mist, or vaporous obscurity, and its reflexes span nearly every major branch of the family with remarkable semantic consistency. Pokorny (IEW 315) reconstructs the root as the primary PIE term for cloud and atmospheric moisture, a reconstruction well supported by the breadth and phonological regularity of its descendants. In Sanskrit, nábhas- means cloud, mist, or sky, appearing already in the Rigveda with cosmological overtones; the Avestan cognate nabah- likewise denotes the sky or atmosphere. Greek nephélē (cloud) and néphos (mass of cloud) preserve the root with characteristic Greek treatment of the labial aspirate, and it is from this Greek line that the astronomical and medical term nebula ultimately descends, though by way of Latin. Latin nebula itself, meaning mist, fog, or cloud, shows the expected development of PIE *bʰ to Latin b, and it was borrowed directly into scientific terminology during the eighteenth century to describe the faint celestial smudges that telescopes were beginning to resolve. The Germanic branch is equally faithful: Old High German nebul and modern German Nebel (fog, mist) continue the root with regular Germanic consonant shifts, while Old English nifol (dark, misty) and the related Old Norse nifl-, familiar from Niflheim, the misty realm of Norse cosmology, attest to its deep presence in northern European culture and myth. Old Irish nél (cloud) and Old Church Slavonic nebo (sky, heaven) round out the picture across Celtic and Balto-Slavic, the latter showing a characteristic semantic broadening from cloud to sky to heaven that recurs independently in several traditions. The consistent meaning across five millennia of attested development makes *nebʰ- one of the more stable items in the reconstructed PIE natural vocabulary, a root whose referent — the visible, drifting, mutable cloud — seems to have resisted the metaphorical pressures that reshaped so many other terms. In modern English, nebula and nebulous are the learned Latin borrowings, while the native Germanic reflex was lost in the transition from Old to Middle English, displaced by the Scandinavian-influenced cloud.
Notes
Pokorny 315. English nebula from Latin.