In modern usage, a céilidh or ceilidh (ˈkeɪlɪ) is a traditional Gaelic

Gaels

The Gaels or Goidels are speakers of one of the Goidelic Celtic languages: Irish, Scottish Gaelic, and Manx. Goidelic speech originated in Ireland and subsequently spread to western and northern Scotland and the Isle of Man....

 social gathering, which usually involves playing Gaelic folk music

Gaelic music

Gaelic music is an umbrella term forthe folk music of the Scottish Highlands and of Ireland . It has also been used for any music written in the Gaelic languages of Scottish Gaelic and Irish. Gaelic music could thus be seen as a type of Celtic music....

 and dancing. It originated in Ireland

Ireland

Ireland is an island to the northwest of continental Europe. It is the third-largest island in Europe and the twentieth-largest island on Earth...

, but is now common throughout the Irish

Irish people

The Irish people are an ethnic group who originate in Ireland, an island in northwestern Europe. Ireland has been populated for around 9,000 years , with the Irish people's earliest ancestors recorded having legends of being descended from groups such as the Nemedians, Fomorians, Fir Bolg, Tuatha...

 and Scottish

Scottish people

The Scottish people , or Scots, are a nation and ethnic group native to Scotland. Historically they emerged from an amalgamation of the Picts and Gaels, incorporating neighbouring Britons to the south as well as invading Germanic peoples such as the Anglo-Saxons and the Norse.In modern use,...

 diaspora

Diaspora

A diaspora is "the movement, migration, or scattering of people away from an established or ancestral homeland" or "people dispersed by whatever cause to more than one location", or "people settled far from their ancestral homelands".The word has come to refer to historical mass-dispersions of...

s. In Scottish Gaelic it is spelled cèilidh (ˈkʲʰeːli) and in Irish

Irish language

Irish , also known as Irish Gaelic, is a Goidelic language of the Indo-European language family, originating in Ireland and historically spoken by the Irish people. Irish is now spoken as a first language by a minority of Irish people, as well as being a second language of a larger proportion of...

 it is spelled céilí (ˈceːlʲiː).
The term is derived from the Old Irish céle (singular) meaning "companion".