An Etymological Dictionary of Astronomy and Astrophysics

Hydrated oxide of iron, mainly Fe₂O₃H₂O, formed on the surface of iron when it is exposed to moisture and air.

Etymology (EN): O.E. rust, related to rudu “redness,” from P.Gmc. *rusta- (cf. O.H.G., Ger. rost, M.Du. ro(e)st), from PIE base *reudh- “red” (cf. Lith. rustas “brownish,” rudeti “to rust;” L. robigo, O.C.S. ruzda “rust”).

Etymology (PE): Zang “rust,” variants žang, zangâr, of unknown origin.