Their ancestor Walter Tirel (died after 1100) is notorious as the killer (although whether the killing was murder or accident is still a matter of debate) of King William Rufus.
In 1169 when Richard de Clare, 2nd Earl of Pembroke, nicknamed Strongbow, invaded Ireland on behalf of Henry II of England, Tyrrel accompanied him.
When de Lacy left Ireland to join the King in France, he made Tyrrel Constable of Trim Castle.
In 1173 the Lordship of Meath was invaded by Ruaidrí Ua Conchobair, High King of Ireland, and Trim Castle was besieged.
In particular, he made a substantial grant of lands in present-day Phoenix Park to the Order of St. John of Jerusalem, whose Irish house was at Kilmainham.