The English langauage has always adopted words from other languages, including the Celtic/Gaelic ones - whisky, for example. The word "ceilidh" when used in an English context means something very different from its Scottish meaning. It was adopted in oder to distinguish a particular style of dancing from other styles. You may wish that a different word had been chosen, but that's the one that has gone into widespread usage.

These distinctions are significant. "Ceilidhs" are different in character, and will probably attract a different audience, from "country dances", "barn dances", "tea dances", "D4D" and all the other descriptions you may come across. Sidmouth puts on a wide variety of dance events of different types and these distinctions are important for those who attend. These words are not synonyms.