Switzerland is officially known by the Latin name "Confoederatio Helvetica" for historical reasons. "Confoederatio" means "confederation" and "Helvetica" is a reference to the Helvetians, a Celtic tribe that lived in Switzerland when the Romans invaded. The English equivalent of the Latin name is "Swiss Confederation."
The name is not an accurate reflection of Switzerland's structure; the state has been a federation since 1848. Switzerland existed, as a true confederation, before 1848. When it became a federation and limited the power of the individual cantons, Switzerland continued to officially call itself a confederation. The international abbreviation of Switzerland is "C.H.," which comes from "Confoederatio Helvetica."