Blimp is an informal term typically applied to non-rigid, helium-filled, airships.
The term 'blimp' is reportedly onomatopoetic, the sound the ship makes when one taps the balloon with a finger. Although there is some disagreement among historians, credit for coining the term is usually given to Lt. A.D. Conningham of the Britsh Royal Navy in 1915.
There is an often repeated, but false, alternative explanation for the term. The erroneous story is that at some time in the early 20th century, the US military had two classes for airships: Type A-rigid, Type B-limp. Hence 'blimp'. In fact, "there was no American 'A-class' of airships as such—all military aircraft, heavier or ligher-than-air were designated with 'A' until the appearance of B-class airships in May 1917. There was an American B airship—but there seems to be no record of any official designation of non-rigids as 'limp' Further, according to the Oxford Dictionary, the first appearance of the word in print was in 1916, in England, a year before the first B-class airship." (from Etymology of 'Blimp' by Dr. A. D. Topping, AAHS Journal, Winter 1963) The perpetuation of this erroneous explanation is an example of an urban legend.
Blimps maintain their form by internal overpressure. Typically, the only solid parts are the passenger car and the tail fins.
A blimp that uses heated air instead of a light gas as lifting medium is sometimes called a hotship.
''See also: airship