Etymology
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piston (n.)

in mechanics, "a movable piece so fitted as to fill the section of a tube and capable of being driven alternately in two directions by pressure on either side," 1704, from French piston "a piston," in Middle French "large pestle," from Old Italian pistone "a piston," variant of pestone "a pestle," from pestare "to pound," from Late Latin pistare, frequentative of Latin pinsere (past participle pistus) "to pound" (see pestle). As a verb, "to move like a piston," from 1930.

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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.

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hot-rod (n.)
also hot rod, 1945, American English, from hot (adj.) + rod (n.), here apparently in a sense of "hunk of metal" (the cars also were called hot iron).
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reciprocating (adj.)

"moving backwards and forwards," 1690s, present-participle adjective from reciprocate (v.). Specifically of machines, "having reciprocating parts," by 1822.

Reciprocating engine. A form of engine in which the piston and piston-rod move back and forth in a straight line, absolutely relative to the cylinder, as in oscillating-cylinder engines: in contradistinction to rotary engine. [Century Dictionary, 1895]
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baguette (n.)
1731, a type of architectural ornament, from French baguette "a wand, rod, stick" (16c.), from Italian bacchetta, literally "a small rod," diminutive of bacchio "rod," from Latin baculum "a stick" (see bacillus). Meaning "a diamond cut long" is from 1926; that of "a long, thin loaf of French bread" is from 1958.
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rhabdomancy (n.)

1640s, "dowsing, use of a divining rod" (especially to find things hidden in the earth, ores or underground water), with -mancy "divination by means of" (from Greek manteia "divination, oracle") + Greek rhabdos "rod, wand; magic wand; fishing rod; spear-shaft; a staff of office; a rod for chastisement; twig, stick." Greek rhabdos is from PIE *wer- (2), base of roots meaning "to turn, bend" (source also of Lithuanian virbas "twig, branch, scion, rod," Latin verbena "leaves and branches of laurel").

The Greek noun was used to represent Roman fasces. Related: Rhabdomantic; rhabdomancer.

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ferule (n.)
"rod or flat piece of wood for punishing children," 1590s, earlier "giant fennel" (early 15c.), from Middle English ferula "fennel plant" (late 14c.), from Latin ferula "reed, whip, rod, staff; fennel plant or stalk" (fennel stalks were used for administering flogging punishment in ancient Roman times) probably related to festuca "stalk, straw, rod."
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goldenrod (n.)
1560s, from golden + rod (n.). So called for its yellow heads.
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perch (n.1)

"rod or pole on which a bird alights and rests," late 13c., originally only "a pole, rod, stick, stake," from Old French perche "unit of linear measurement" (5.5 yards), also "measuring rod, pole, bar" used to measure this length (13c.), from Latin pertica "pole, long staff, measuring rod," which is related to Oscan perek "pole," Umbrian perkaf "twigs, rods." Meaning "a bar fixed horizontally for a hawk or tame bird to rest on" is attested from late 14c.; this led to the general sense of "any thing that any bird alights or rests on" (late 15c.). Figurative sense of "an elevated or secure position" is recorded from 1520s.

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perch (n.3)

"measure of land equal to a square lineal perch" (usually 160 to the acre), late 14c., earlier "land-measuring rod" (c. 1300), from Old French perche "unit of linear measurement" (5.5 yards), also "measuring rod, pole, bar" used to measure this length (13c.), from Latin pertica "pole, long staff, measuring rod," which is related to Oscan perek "pole," Umbrian perkaf "twigs, rods." The same word as perch (n.1).

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