Definition:Imperial/Length/Rod, Pole or Perch/Linguistic Note
Linguistic Note on Rod, Pole or Perch
The rod, pole and perch are all synonyms for the same (archaic) unit of land measurement.
The terms arise from the days of ploughing in mediaeval times.
While the ploughman handled the plough, his assistant controlled the oxen, by means of a stick long enough to reach all the oxen from behind the plough.
This stick was the original rod, pole or perch, and its standard length (from the back of the plough to the front of the oxen) was a convenient way to measure a field.
The word perch derives from the Latin pertica, which itself also means staff or pole.
In modern times, the only time you are likely to see the term rod, pole or perch is in a conversion table, where that is how it is traditionally listed.