Is there a Gaelic word sith and if so the meaning?

Sìthe (pronounced "shee") is a Gaelic word that originally meant "peace" or "fairy mound." It is often used in reference to the sídhe, a race of supernatural beings in Irish mythology who live in the hills and mounds of Ireland. The sídhe are often depicted as being beautiful, wise, and powerful, and they are said to be able to grant wishes and protect people from harm.