The Lord Lieutenant of Ireland (plural: Lords Lieutenant) is the name of a political office (job). It was the representative of the King and head of the Irish executive (government) between 1171 and 1922. The term is always pronounced as 'Lord Lef-tenant of Ireland'.
Other words used for this office were Judiciar in the early mediaeval period and Lord Deputy as late as the 17th century. The people in this job were often also called viceroy, from the French vice roi or deputy king.
In the Middle Ages some Lord Lieutenants had been Irish noblemen. After that only noblemen from Great Britain worked in this job.