Fans of the long-running TV series M*A*S*H know that its initials stand for Mobile Army Surgical Hospital. MASH units “were first established in August 1945, and were deployed during the Korean War and later conflicts. The U.S. Army deactivated the last MASH unit on February 16, 2006,” according to Wikipedia.
A MASH was not the first portable hospital, however. For example, in the late 1700s the French used what was called (hôpital) ambulant. This was a mobile or field hospital, according to the Online Etymology Dictionary. It literally meant “hospital walking.” (In French an adjective most often comes after a noun.)
During the Crimean War in the 1850s, the word became common in English and its meaning went from field hospital to a "vehicle for conveying wounded from field,” according to the same dictionary.
Two synonyms for walk, amble and ambulate, share etymological roots with ambulance.
Illustration special to the Sentinel