Etymology: < Middle French, French nitre (late 12th cent. in Old French) < classical Latin nitrum < ancient Greek νίτρον (also λίτρον ), probably ultimately < Egyptian nṯrj . It is not clear whether the Greek forms were direct borrowings from Egyptian, or whether they entered Greek via a third, possibly Semitic, language (compare Hebrew neṯer (Proverbs 25:20, Jeremiah 2:22), Akkadian nitiru , nitru (attested from the first millennium bc, perhaps < Egyptian), Syriac neṯrā , Aramaic niṯrā (attested in unvocalized form as ntr' , &c.5th cent. bc). Compare Italian nitro (a1342), Spanish nitro (1555), Portuguese nitro . Compare natron n., and earlier nitrum n.A major of source of natron in the ancient world was Egypt, and the principal source in Egypt was the Wadi Natrun. There are several Egyptian words for natron, one of which is nṯrj . This word is attested in the Pyramid texts (Old Egyptian), and is probably < nṯrj divine, sacred (since one was purified, as on entering a temple, or made divine by mummification, using natron). Although the Egyptian word is attested in all periods, there is a possibility that all forms of the Greek word came via Semitic languages. Ancient writers used the etyma of nitre for various alkaline salts and saline efflorescences, chiefly natron (i.e. naturally occurring soda: the Egyptian variety has been shown to consist of sodium carbonate and sodium bicarbonate with sodium chloride and sodium sulphate as impurities), but probably also saltpetre and sal ammoniac, and occasionally potash. These words were also used for a kind of soap made from natron and oil; this latter is the meaning alluded to in sense 2a. The transition from the meaning ‘natron’ to the meaning ‘saltpetre’ apparently resulted from confusion: the use of post-classical Latin sal nitri for saltpetre (compare sal-nitre n.) can be traced at least to the works of Ramón Lull (c1300), and by the late 16th cent. nitre was used more often for saltpetre than for soda (though sodium and potassium nitrates were not clearly distinguished until the 18th cent.). Compare:1565 J. Hall Expositiue Table 104 in tr. Lanfranc Most Excellent Woorke Chirurg. Albei (as most true it is) that our Salte petre is not νίτρον καὶ λίτρον of Dioscorides, Galen, Plinie, and other auncient wryters, whiche is naturall, commyng of certeyne waters in lakes: and should be lyght, rose coloured or whyte, cleauying or openyng it selfe into many pores lyke a spungy substance. But our Salt peter (which is artificiall) is glisteryng whyte, (if it be good) or els blackyshe, (if it be not made perfecte by boylyng) solide and weyghty... Surely is it euident, that Lanfranke and many others right learned, both of his tyme and long since, ment according to the vulgar opinion, (though not without great errore,) that which hath ben commonly called sal petrae, when they wrote Sal Nitrum.

Etymology: < nitre n. Compare earlier nitred adj.