[...] The terms gwoka and ka seem to have been used only recently and, would appear to have originated from the Capesterre region in Guadeloupe.
There are two synonyms, bamboula and gwotanbou - the latter is more commonly used by the elderly.
The instrument both words describe is a membranophone covered with goatskin. The body of this instrument is one of those barrels which, until recently, were used to store salt meat being shipped to the French West Indies. [...]
(Marie-Céline Lafontaine : Unité et diversité des musiques traditionnelles guadeloupéennes, in Les Musiques guadeloupéennes, Editions Caribéennes, 1988, page 73.)

[...] The same word exists in Haiti, also describing a secular drum, type of music and dance steps. It has also been proven that it describes a drum in New Orleans and in Martinique dating from the end of the 19th century.
...
The term gro tanbou (big drum) was widely used in the past together with banboula to describe the gro ka drum. It would appear that the term "ka" was more frequently used in a particular area of the island, namely Capesterre, and at present is used everywhere. The available literature seems to confirm this piece of information [...]
(Marie-Céline Lafontaine, Musique et société aux Antilles : "Balakadri" ou le bal de quadrille au commandement de la Guadeloupe. Présence Africaine 121/122 : 72-108, page 76.)

The origin of the term gwoka
The term ka comes from "Gros Quart" which described one of the huge barrels of salt meat or wine in used during the colonial era. Similarly, it could also come from the word "Caques", a term used to describe the barrels used for storing salted herring, a staple food during colonial times.
From the 1960s onwards, another etymology was offered, that of "N'Goka" - refering to a small drum originating from Central Africa (mentioned by Simone Schwartz-Bart in Pork and green bananas, Gwoka as seen by... / The writers).
Till this day, neither of these three theories have been proven. Several articles and chapters from various works have been devoted to such (see References / Books, Gabaly, Uri...).