Adam Clarke's Commentary on the Bible

Verse 18 (Isaiah 1:18)

Though your sins be as scarlet - שני shani , "scarlet or crimson," dibaphum, twice dipped, or double dyed; from שנה shanah , iterare , to double, or to do a thing twice. This derivation seems much more probable than that which Salmasius prefers from שנן shanan , acuere , to whet, from the sharpness and strength of the color, οξυφοινικον ; תלע tela , the same; properly the worm, vermiculus , (from whence vermeil), for this color was produced from a worm or insect which grew in a coccus or excrescence of a shrub of the ilex kind, (see Plin. Nat. Hist. 16:8), like the cochineal worm in the opuntia of America. See Ulloa's Voyage book v., chap. ii., note to page 342. There is a shrub of this kind that grows in Provence and Languedoc, and produces the like insect, called the kermes oak, (see Miller, Dict. Quercus), from kermez , the Arabic word for this color, whence our word crimson is derived.

" Neque amissos colores

Lana refert medicata fuco

- Adam Clarke's Commentary on the Bible