Is it farther or further?
late 14c., probably representing a merger of Old Norse steina "to paint" and a shortened form of Middle English disteynen "to discolor or stain," from Old French desteign-, stem of desteindre "to remove the color," from des- (from Latin dis- "remove;" see dis-) + Old French teindre "to dye," from Latin tingere (see tincture). Related: Stained; staining. Stained glass is attested from 1791.
1560s, from stain (v.).
A reagent or dye that is used for staining microscopic specimens.
A procedure in which a dye or a combination of dyes and reagents is used to color the constituents of cells and tissues.