An Etymological Dictionary of Astronomy and Astrophysics

Natural mixture of liquid hydrocarbons and other organic compounds that include crude oil, refined products obtained from the processing of crude oil, and natural gas liquids.

Etymology (EN): M.L. petroleum literally “rock oil,” from L. petra “rock,” from Gk. → petro-, + oleum “oil.”

Etymology (PE): Naft, from Mid.Pers. npt “moist, damp;
naphtha,” nmb “moisture,” from which derives Mod.Pers. nam “humidity, moisture;” Av. napta- “moist,” nabah- “cloud; sky;”
cf. Skt. nábhas- “moisture, cloud, mist;” PIE base *nebh- “cloud, vapor, fog, moist, sky” (Gk. nephos “cloud, mass of clouds,” nephele “cloud;” L. nebula “mist,” nimbus “rainstorm, rain cloud;” O.H.G. nebul; Ger. Nebel “fog;” O.E. nifol “dark”). The link between “water, moisture” and “naphta” is suggested to be
the natural gas or oil seepages surfacing through water. In fact many of the Zoroastrian fire-temples were located in areas which contained large petroleum leakages, such as those in Khuzestân
and at Surakhany near Baku.