The tank is called the tank in English (and in French, the char de combat - combat tank) because of its development. At first, tanks were envisaged as warships on land and the group tasked to design them was the Landships Committee. The first tanks were actually a scheme by the British Navy, not the Army. Eventually, once the Mark I tank was designed, it was codenamed as a tank because its production was disguised as the production of water tanks. This name was adopted in late 1915 and the Landships Commitee was later renamed the Tank Supply Committee.

However in Nordic and German languages the word used is "armoured vehicle"; Strisdvagn in Swedish but most famously Panzerkampfwagen in German (armoured battle vehicle). I'm sure someone will give a better answer than this, but this is the gist of it.

The word has spread to other languages as a loanword; "char" is the French word for tank, in Russian, tank is literally "tank" but its adjective form is "tankoviy". In Spanish and Italian the word is "combat vehicle" or carro de combate / carro da combattimento although apparently in Spanish you can also use ... tanque. AFAIK in Japanese the word is tanku (similar in Korean and Chinese too) and in Hebrew the word is tank too (I think - the transliteration seems dodgy.) The only real country today that produces its own main battle tanks whose language uses a word not derived from the English tank is therefore Germany and Italy although it is doubtful if Italy will produce a main battle tank again.

Edit: and what would this be without a source! Armoured Fighting Vehicles of the World Series 3, Tanks Mark I-V by Duncan Crow, Chris Ellis & Peter Chamberlain, for the history behind the way the British adopted the name tank and the development of their first tanks. If you are interested I can detail the story further for you.