gold-leaf (n.)

"precious metal noted for its color, luster, malleability, and freedom from rust or tarnish," Old English gold, from Proto-Germanic *gulthan "gold" (source also of Old Saxon, Old Frisian, Old High German gold, German Gold, Middle Dutch gout, Dutch goud, Old Norse gull, Danish guld, Gothic gulþ), from PIE root *ghel- (2) "to shine," with derivatives denoting gold (the "bright" metal).

The root is the general Indo-European one for "gold," found in Germanic, Balto-Slavic (compare Old Church Slavonic zlato, Russian zoloto, "gold"), and Indo-Iranian. Finnish kulta is from German; Hungarian izlot is from Slavic. For Latin aurum see aureate. Greek khrysos probably is from Semitic.

From Homer on through Middle English, "red" often is given as a characteristic color of pure gold or objects made from it. This is puzzling, but it might stem from an ancient practice of testing the purity of gold by heating it; in Middle English red gold was "pure gold" (c. 1200).

Nay, even more than this, the oftener gold is subjected to the action of fire, the more refined in quality it becomes; indeed, fire is one test of its goodness, as, when submitted to intense heat, gold ought to assume a similar colour, and turn red and igneous in appearance; a mode of testing which is known as "obrussa." [Pliny, "Natural History," 33.19]

Old English leaf "leaf of a plant, foliage; page of a book, sheet of paper," from Proto-Germanic *lauba- (source also of Old Saxon lof, Old Norse lauf, Old Frisian laf, Dutch loof, Old High German loub, German Laub "foliage, leaves," Gothic laufs "leaf, foliage"), perhaps from PIE *leub(h)- "to peel off, strip or break off" ((source also of Old Irish luib, "herb," lub-gort "garden;" Albanian labë "rind, cork;" Lithuanian luba "plank, board;" Russian lob "forehead, brow," Czech leb "skull;" Lithuanian luobas "bast," Latvian luobas "peel," Russian lub "bast;" Old Norse lyf "medicinal herbs," Old English lybb "poison; magic").

Related to lodge and lobby; for another PIE root see folio. Extended late 14c. to very thin sheets of metal (especially gold). Compare Lithuanian lapas "leaf," from a root also in Greek lepos "bark," lepein "to peel off." Also applied to flat and relatively broad surfaces, especially of flexible or mounted attachments; meaning "hinged flap on the side of a table" is from 1550s. To turn over a (new) leaf (1590s; 1570s as turn the leaf) "begin a new and better course of life" is a reference to the book sense. Among insects, leaf-hopper is from 1847; leaf-cutter from 1816.