realgarn.

Etymology: < post-classical Latin realgar (from 13th cent. in British and continental sources), ultimately < Arabic rahj al-ġār , literally ‘dust of the cave’ < rahj dust + al- the + ġār cave (see note). Compare Middle French riagal (c1330), Middle French reagal (c1378), rialgal (1382), realgar (1495), French réalgar , †réagal , †réalgal , Old Occitan realgar (c1300), Catalan realgar (end of the 13th cent.), Spanish rejalgar (13th cent.), Italian realgar , †realgare (15th cent.). Compare resalgar n., rosaker n.In form realgal apparently after French réalgal. It has frequently been suggested (e.g. by J. J. Hess in Vox Romanica 2 (1937) 475) that Arabic rahj al-ġār may be a transmission error for rahj al-fār, literally ‘rat powder’ ( < rahj dust + al- the + fār mouse, rat), the mineral being so called because it was used as rat poison. Although this use of the mineral is indeed mentioned by some contemporary Arabic sources, where the mineral is called samm al-fār, literally ‘rat poison’, other Arabic texts (where the mineral is called rahj al-ġār) state or imply that it is found in silver mines, and the Arabic form with initial ġ in the second element of the compound is too well attested to make the suggestion of a mere scribal error seem likely; it is more plausible that the form rahj al-fār resulted from an alteration of rahj al-ġār after its popular, non-technical synonym samm al-fār.