So there's French Guiana, and then Guyana.
Both are part of the Guianas (or Guyanas/Guayanas).
The "Guiana" region (land of waters), was home to the Arawak and Carib peoples, and then there was a colonial scramble between the Dutch, English and French over the last half millennia-- each respectively took over some portion and then slapped their names on it.
Guyana is independently english speaking because they were colonized by the British- centuries ago it used to go by British Guiana.
French Guiana is basically an overseas department of France.
