- rod (n.)
- Old English rodd "a rod, pole," related to Old Norse rudda "club," of unknown origin. 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 "correction, punishment" from notion of beating someone with a stick. As a unit of measure (5.5 yards or 16.5 feet, also called perch or pole) first attested mid-15c. As a measure of area, "a square perch," from late 15c. Meaning "light-sensitive cell in a retina" is from 1866, so-called for its shape. Slang meaning "penis" is recorded from 1902; that of "gun, revolver" is from 1903.