Irish language
The Irish language (Gaeilge) was a language spoken by Human Celtics that originated in the Earth region of Ireland.

Irish language signage was used in the holodeck village of Fair Haven. ().

For example:
Cuan Soineanta: fair (weather) harbor / refuge. (Irish name for town of Fair Haven.)
Oifig an Phoist: post office
Fáilte: Welcome (On sign outside The Ox and Lamb.)
Fáilte a Thaistealaí Thuirseach: Welcome Weary Traveler.

Siopa Búistéara: butcher's shop

Sayings
Céad míle fáilte (pronounced "Cayd mila fallcha") was an old Irish saying that means "a hundred thousand welcomes." 

Michael Sullivan, the local bartender in the Fair Haven holodeck program, greeted Captain Kathryn Janeway (known to him as Katie O'Clare) with it when she visited the Fair Haven pub after initiating an open door policy for the program. ()

"Sláinte" ("health") was a phrase said in Irish when sharing a drink, similar to the English "cheers". ()

External links

de:Irisch
fr:Gaélique Irlandais
Earth languages