According to Krysstal, they are referred to as borrowed words, or words loaned from other languages. I am not sure if there is a word or expression that means that the word is borrowed back.
Some of the Greek words that fit this category, though, include:
Australia - Originally meaning southern, and now referring to the country.
Catholic - Originally meaning universal, and now referring to the religion. Note that the Greek Orthodox bible still uses the original meaning of this word. I believe there are some disciplines that also use the original meaning of this word.
Democracy - Originally meaning state of the people, and now referring to the political paradigm. The same can be said for politics, which comes from the word politis meaning man of the people. I much rather prefer Larry Hardiman's definition of the word, though.
Mesopotamia - Originally meaning between the rivers, and now referring to the ancient region now part of Iraq.
Telephone - Originally meaning far voice, and now referring to the communication device.
Note that the above link provides a list of words that the English language has borrowed from other languages.