1560s, from golden + rod (n.). So called for its yellow heads.
Entries linking to goldenrod
golden adj.
c. 1300, "made of gold," from gold (n.) + -en (2); replacing Middle English gilden, from Old English gyldan. Gold is one of the few Modern English nouns that form adjectives meaning "made of ______" by adding -en (as in wooden, leaden, waxen, olden); those that survive often do so in specialized senses. Old English also had silfren "made of silver," stænen "made of stone," etc.
From late 14c. as "of the color of gold." Figurative sense of "excellent, precious, best, most valuable" is from late 14c.; that of "favorable, auspicious" is from c. 1600. Golden mean "avoidance of excess" translates Latin aurea mediocritas (Horace). Golden age "period of past perfection" is from 1550s, from a concept found in Greek and Latin writers; in sense of "old age" it is recorded from 1961. San Francisco Bay's entrance channel was called the Golden Gate by John C. Fremont (1866). The moralistic golden rule earlier was the golden law (1670s).
Whatsoever ye would that men should do to you, do ye even so to them [Matthew vii.12]
Do not do unto others as you would that they should do unto you. Their tastes may not be the same. [George Bernard Shaw, 1898]
rod n.
Middle English rod, rodde, "a stick of wood," especially a straight cutting from a woody plant, stripped of twigs, and having a particular purpose" (walking stick, wand of office, instrument of punishment), from Old English rodd "a rod, pole," which is probably cognate with Old Norse rudda "club," from Proto-Germanic *rudd- "stick, club," from PIE *reudh- "to clear land." Other sources formerly consider it to correspond to the continental words under rood.
As a long, tapering elastic pole for fishing, from mid-15c. Figurative sense of "offshoot" (mid-15c.) led to Biblical meaning "scion, tribe." As an instrument of punishment, attested from mid-12c.; also used figuratively for "any sort of correction or punishment" (14c.). In mechanics, "any bar slender in proportion to its length" (1728).
As a unit of linear measure (5½ yards or 16½ feet, also called perch or pole) attested from late 14c., from the pole used to mark it off. As a measure of land area, "a square perch," from late 14c., the usual measure in brickwork. Meaning "light-sensitive cell in a retina" is by 1837, so-called for their shape. Slang meaning "penis" is recorded from 1902; that of "handgun, pistol, revolver" is by 1903.