From the Temple Bar Pub website:
"In 1599, Sir William Temple, a renowned teacher and philosopher, entered the service of the Lord Deputy Of Ireland. In 1609 Temple was made Provost of Trinity College, Dublin and Master Chancery in Ireland and moved to this country.
Sir William Temple built his house and gardens on newly reclaimed land here on the corner of Temple Lane and the street called Temple Bar. In 1656, his son, Sir John Temple, acquired additional land, which with reclamation made possible by the building of a new sea wall, allowed the development of the area we now know as Temple Bar.
In the 17th century ‘Barr’ (later shortened to Bar) usually meant a raised estuary sandbank often used for walking on. Thus the river Liffey embankment alongside the Temple family's plot became known as Temple's Barr or simply Temple Bar. Later this evolved into the present thoroughfare connecting this whole area from Westmoreland Street to Fishamble Street."