TONNEAU
Etymology
Noun
tonneau (plural tonneaus or tonneaux)
The rear body or compartment of some types of motor vehicle, especially one containing seats for passengers.
An old-style open passenger vehicle with a tonneau (rear compartment with seats).
Clipping of tonneau cover.
Source: Wiktionary
Ton`neau", n.; pl. Tonneaux (#). [F.]
1. In France, a light-wheeled vehicle with square or rounded body and
rear entrance.
2. (Automobiles) Orig., the after part of the body with entrance at
the rear (as in vehicle in def. 1); now, one with sides closing in
the seat or seats and entered by a door usually at the side, also,
the entire body of an automobile having such an after part.
3. = Tonne.
Source: Webster’s Unabridged Dictionary 1913 Edition