The change from M to V is normal, Mh is pronounced V. Vaddock (with its synonyms Waddock, Weddick etc., and also Maddox) is a distinct surname Mac Mhadoc is that of a family which claims descent from the MacMurroughs and so is of Gaelic-Irish not Norman origin. They were formerly called MacVaddock in English, and mediaeval and early modern records contain many references to people of the name and to "MacVadog's country" in Co. Wexford and Co. Kilkenny; and in his official report on the state of the country in 1579 Sir Nicholas Mally speaks of MacEvado, chief of his name. Richard Madock, gent, of Townhely (Tinahely) was a Co. Wicklow Jacobite outlawed under William 111.
The Williamite War in Ireland—also called the Jacobite War in Ireland, the Williamite-Jacobite War in Ireland and in Irish as Cogadh an Dá Rí (meaning "War of the Two Kings")—was a conflict between Catholic King James II and Protestant King William of Orange over who would be King of England, Scotland and Ireland. The cause of the war was the deposition of James II as King of the Three Kingdoms by William (who was married to James' daughter Mary II) in 1688.
James was supported by the mostly-Catholic "Jacobites" in Ireland and hoped to use the country as a base to regain his Three Kingdoms. He was given military support by France to this end. For this reason, the War became part of a wider European conflict known as the Nine Years War. Some Protestants of the established Church in Ireland also fought on the side of King James.
James was opposed in Ireland by the mostly Protestant, "Williamites", concentrated in the north of the country. William landed a multi-national force in Ireland, composed of English, Scottish, Dutch, Danish and other troops, to put down Jacobite resistance. James left Ireland after a reverse at the Battle of the Boyne in 1690 and the Irish Jacobites were finally defeated after the Battle of Aughrim in 1691