I think in Australia they reversed it some. They used to call freshwater turtles tortoises.OMG. So true. At the office everybody jokes with me because I always correct them when they ask how my "turtles" are doing.
However, as above posters have said, in many countries/languages there is one common word. If I'm not mistaken, I believe some English speaking countries have one common word for torts/turtles/terrapins.
I believe technically all tortoises are in fact turtles. But of course not all turtles are tortoises.