Middle English rode, "a cross; a crucifix," especially a large one, from Old English rod "cross," especially that upon which Christ suffered, from Proto-Germanic *rod- (source also of Old Saxon ruoda "stake, pile, cross," Old Norse roða, Old Frisian rode, Middle Dutch roede, Old High German ruota, German Rute "rod, pole"), which is of uncertain origin. Perhaps it shares a PIE root with Latin ratis "raft," retae "trees standing on the bank of a stream;" Old Church Slavonic ratiste "spear, staff;" Lithuanian reklės "scaffolding," but de Vaan is doubtful. Probably not connected with rod.
Also in Old English "a pole;" and in Middle English also a local measure varying from 6 to 8 yards and a square measure of land.
measure of length, Old English gerd (Mercian), gierd (West Saxon) "rod, staff, stick; measure of length," from West Germanic *gazdijo, from Proto-Germanic *gazdjo "stick, rod" (source also of Old Saxon gerda, Old Frisian ierde, Dutch gard "rod;" Old High German garta, German gerte "switch, twig," Old Norse gaddr "spike, sting, nail"), from PIE root *ghazdh-o- "rod, staff, pole" (source also of Latin hasta "shaft, staff"). The nautical yard-arm retains the original sense of "stick."
Originally in Anglo-Saxon times a land measure of roughly 5 meters (a length later called rod, pole, or perch). Modern measure of "three feet" is attested from late 14c. (earlier rough equivalent was the ell of 45 inches, and the verge). In Middle English and after, the word also was a euphemism for "penis" (as in "Love's Labour's Lost," V.ii.676). Slang meaning "one hundred dollars" first attested 1926, American English. Middle English yerd (Old English gierd) also was "yard-land, yard of land," a varying measure but often about 30 acres or a quarter of a hide.
1757, "a rod used in ramming" (the charge of a gun or other firearm), from ram (v.) + rod (n.). Used figuratively for straightness or stiffness by 1939; also figurative of formality or primness (ramroddy, 1886). The verb in the figurative meaning "to force or drive as with a ramrod" is by 1948. Related: Ramrodded; ramrodding.
Earliest attested sense in English is now-obsolete meaning "male member, penis" (c. 1400). Modern sense is from the notion of within the verge (c. 1500, also as Anglo-French dedeinz la verge), i.e. "subject to the Lord High Steward's authority" (as symbolized by the rod of office), originally a 12-mile radius round the king's court. Sense shifted to "the outermost edge of an expanse or area." Meaning "point at which something happens" (as in on the verge of) is first attested c. 1600. "A very curious sense development." [Weekley]
in ancient Greece or Rome, "herald's staff," 1590s, from Latin caduceus, alteration of Doric Greek karykeion "herald's staff," from kēryx (genitive kērykos) "a herald," probably a Pre-Greek word. Token of a peaceful embassy; originally an olive branch. Later especially the wand carried by Mercury, messenger of the gods, usually represented with two serpents twined round it and wings. Related: Caducean.
The caduceus is a symbol of peace and prosperity, and in modern times figures as a symbol of commerce, Mercury being the god of commerce. The rod represents power; the serpents represent wisdom; and the two wings, diligence and activity. [Century Dictionary]
Sometimes used mistakenly as a symbol of medicine by confusion with the Rod ofAsclepius, Greek god of medicine, which also features a serpent entwined about a rod but only a single serpent.
1847, plural of Modern Latin bacterium, from Greek bakterion "small staff," diminutive of baktron "stick, rod, staff, cudgel." So called because the first ones observed were rod-shaped. Introduced as a scientific word 1838 by German naturalist Christian Gottfried Ehrenberg. A classical plural sometimes also erroneously used as a singular.
The Greek word is from a PIE *bak- "staff used for support, peg" (compare Latin baculum "rod, walking stick;" Irish bacc, Welsh bach "hook, crooked staff;" Middle Dutch pegel "peg, pin, bolt"). De Vaan writes, "Since *b was very rare in PIE, and Celtic shows an unexplained geminate, we are probably dealing with a loanword from an unidentified source."
1590s, "cross-shaft, straight rod or bar," from Latin radius "staff, stake, rod; spoke of a wheel; ray of light, beam of light; radius of a circle," a word of unknown origin. Perhaps related to radix "root," but de Vaan finds that "unlikely." The classical plural is radii.
The geometric sense of "straight line drawn from the center of a circle to the circumference" is recorded from 1650s. Meaning "circular area of defined distance around some place" is attested from 1853. As the name of the shorter of the two bones of the forearm from 1610s in English (the Latin word had been used thus by the Romans).