from
Bouvier's Law Dictionary, Revised 6th Ed (1856)
COMMON PLEAS. The name of a court having jurisdiction generally of civil
actions. For a historical account of the origin of this court in England,
see Boote's Suit at Law, 1 to 10. Vide Common Bench and Bench.
2. By common pleas, is also understood, such pleas or actions as are
brought by private persons against private persons; or by the government,
when the cause of action is of a civil nature. In England, whence we derived
this phrase, common pleas are so called to distinguish them from pleas of
the crown. (q.v.)