"sulfur in a solidified state," Old English brynstan, from brin- stem of brinnen "to burn" (from Proto-Germanic *brennan "to burn," from PIE root *gwher- "to heat, warm") + stan (see stone (n.)). In Middle English the first element also recorded as brem-, brom-, brum-, bren-, brin-, bron-, brun-, bern-, born-, burn-, burned-, and burnt-. Formerly "the mineral sulfur," now restricted to biblical usage.
The Lord reynede vpon Sodom and Gomor brenstoon and fier. [Wycliff's rendition (1382) of Genesis xix.24]
The Old Norse cognate compound brennusteinn meant "amber," as does German Bernstein.