Irish: Gleann na gCaorach
The name of the village is from the Irish Gleann na gCaorach meaning 'Glen of the Sheep'.
On early 20th century maps, Glenageary and Sallynoggin are considered to be the same place and it was not until the building of local authority houses in the late 1940s and 1950s in the townlands of Honeypark and Thomastown by Dún Laoghaire Borough Corporation that a clear distinction between Sallynoggin and Glenageary was created.
Until the late 1940s, Glenageary, like much of the southern County Dublin, consisted mostly of large manor estates - each comprising a large house, some woodland and cultivated or landscaped fields. Since then it has been extensively redeveloped. Most of the original manors have been demolished and low-density housing developments built.
Glenageary has one church, which is of the Church of Ireland: St Paul's at the junction of Adelaide and Silchester Roads. It was opened in 1868.
- Pearson, Peter (1998). Between the Mountains and the Sea. The O'Brien Press. ISBN 0-86278-582-0.