The term was first used for the coaches built by coach-builder J. Stephen Abbot and wheelwright Lewis Downing of the Abbot-Downing Company in Concord, New Hampshire, but later to be sometimes used generically.
Like their predecessors, the Concords employed a style of suspension and construction particularly suited to North America's early 19th century roads.
The swaying is accepted by passengers for the shock absorbing action of the leather straps and for the way the special motion eases the coach over very rough patches of roadway.
This suspension, which was developed by Philip de Chiese in the 17th century, was long replaced by steel springs in England.
The Abbot-Downing Company, however, continued making these coaches for over 70 years, well after most their competitors, and the name became used as a generic term.
Passengers on the center bench had no backrest but steadied themselves with a broad leather harness suspended across the coach by straps from the roof.
The driver or coachman has to sit slightly askew and brace himself with the aid of a steeply angled footboard.
He has to bend his arms and elbows to constantly compensate, and his body always leans slightly forward.