Lexical Definition

‎נֶתֶר‎ nether (neh'-ther) lye ^H:N-M
from ‎נָתַר‎

nitre.

• mineral potash (so called from effervescing with acid)

1) natron, nitre, soda, carbonate of soda

Brown-Driver-Briggs

‎נֶ֫תֶר‎ noun [masculine] natron, or carbonate of soda, a mineral alkali (Late Hebrew = Biblical Hebrew; Aramaic ‎נִתְרָא‎, ; compare Greek νίτρον, λίτρον, Latin nitrum (see Lexicons)); — ‎אִםתְּֿכַבְּסִי בַּנֶּתֶר‎ Jer 2:22 though thou wash thyself with natron (figurative; || ‎בֹּרִית‎; on use of 'nitrum' for handwashing among Greeks see Meineke^{Fragm. Comicorum ii. 638}); ‎חֹמֶץ עַלנָֿ֑תֶר‎ Prov 25:20 (figurative of the incompatible).

Brown-Driver-Briggs References