ambul-, ambulat-, -ambulate, -ambulating, -ambulation -ambulator, -ambulatory, -ambulant, -ambulic, -ambulism, -ambulist (Latin: walk, take steps, move around; from "to wander, to go astray").
"Ambulance" was borrowed from French hopital ambulant, mobile hospital, or literally, "walking hospital," from Latin ambulantem and ambulare, "to walk."
Historically, soldiers wounded in battle usually stayed where they fell until it was dark or until the end of some particular combat when they could be carried or dragged off for treatment.
This situation didn't change until 1240, when Italy's Misericordia di Firenze, the first known emergency-care service, was founded. Although primitive horse-drawn conveyances for the wounded made occasional appearances — at the Battle of Málaga in 1487, for example — it wasn't until 1792 that ambulances became a regular part of the battlefield scene. It was at this time that Baron Dominique-Jean Larrey, a French army surgeon, introduced what he called the ambulances volantes, or "flying field hospitals." Such conveyances were covered, portable litters filled with bandages to stop the flow of blood and to bind the wounds of soldiers on the battlefield. The transporter was also called the hopital ambulant; that is, "walking" or "traveling hospital."
One of the first "modern" ambulance systems appeared during the American Civil War, when Dr. Jonathan Letterman, medical director of the Army of the Potomac, assigned two horse-drawn ambulances to every regiment of 500 infantrymen. The Geneva Convention, in 1864, recognized military ambulances, declaring that the vehicles, the wounded they carried, and the medics that operated them should be considered and treated as neutrals.
(New York: The Philosophical Library, 1943).
Dictionary of Word Origins by John Ayto
(New York: Little, Brown and Co., 1990).
Morris Dictionary of Word and Phrase Origins by william and Mary Morris
(New York: Harper & Row, 1971).